Revive the project

app/src/main/java/org/solovyev/android/Check.java

@@ -42,7 +42,8 @@ public final class Check {
     private static boolean isJunit() {
         final StackTraceElement[] stackTrace = currentThread().getStackTrace();
         for (StackTraceElement element : stackTrace) {
-            if (element.getClassName().startsWith("org.junit.")) {
+            String className = element.getClassName();
+            if (className.startsWith("org.junit.") || className.startsWith("org.robolectric.")) {
                 return true;
             }
         }

app/src/main/java/org/solovyev/android/calculator/ActivityLauncher.java

@@ -27,7 +27,7 @@ import android.app.Application;
 import android.content.Context;
 import android.content.Intent;
 import android.net.Uri;
-import android.support.annotation.NonNull;
+import androidx.annotation.NonNull;
 import android.text.TextUtils;
 import dagger.Lazy;
 import jscl.math.Generic;

app/src/main/java/org/solovyev/android/calculator/AdView.java

@@ -9,10 +9,12 @@ import android.view.Gravity;
 import android.view.View;
 import android.widget.FrameLayout;
 
+import androidx.annotation.NonNull;
 import com.google.android.gms.ads.AdListener;
 import com.google.android.gms.ads.AdRequest;
 import com.google.android.gms.ads.AdSize;
 
+import com.google.android.gms.ads.LoadAdError;
 import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
 
@@ -81,11 +83,6 @@ public class AdView extends FrameLayout {
         admobView.setAdListener(admobListener);
 
         final AdRequest.Builder b = new AdRequest.Builder();
-        b.addTestDevice(AdRequest.DEVICE_ID_EMULATOR);
-        if (BuildConfig.DEBUG) {
-            // LG Nexus 5
-            b.addTestDevice("B80E676D60CE6FDBE1B84A55464E3FE1");
-        }
         admobView.loadAd(b.build());
     }
 
@@ -127,7 +124,7 @@ public class AdView extends FrameLayout {
         }
 
         @Override
-        public void onAdFailedToLoad(int errorCode) {
+        public void onAdFailedToLoad(@NonNull LoadAdError loadAdError) {
             if (adView != null) {
                 adView.hide();
                 adView = null;

app/src/main/java/org/solovyev/android/calculator/App.java

@@ -36,13 +36,8 @@ import android.net.Uri;
 import android.os.Build;
 import android.os.IBinder;
 import android.os.Looper;
-import android.support.annotation.ColorInt;
-import android.support.annotation.NonNull;
-import android.support.v4.app.DialogFragment;
-import android.support.v4.app.Fragment;
-import android.support.v4.app.FragmentManager;
-import android.support.v4.app.FragmentTransaction;
-import android.support.v7.view.ContextThemeWrapper;
+import androidx.annotation.ColorInt;
+import androidx.annotation.NonNull;
 import android.text.Spannable;
 import android.text.SpannableString;
 import android.text.style.ForegroundColorSpan;
@@ -54,6 +49,11 @@ import android.view.ViewGroup;
 import android.view.inputmethod.InputMethodManager;
 import android.widget.ArrayAdapter;
 
+import androidx.appcompat.view.ContextThemeWrapper;
+import androidx.fragment.app.DialogFragment;
+import androidx.fragment.app.Fragment;
+import androidx.fragment.app.FragmentManager;
+import androidx.fragment.app.FragmentTransaction;
 import org.solovyev.android.Check;
 import org.solovyev.android.calculator.floating.FloatingCalculatorService;
 
@@ -312,7 +312,7 @@ public final class App {
 
     @Nonnull
     public static <T> ArrayAdapter<T> makeSimpleSpinnerAdapter(@NonNull Context context) {
-        return new ArrayAdapter<>(context, R.layout.support_simple_spinner_dropdown_item);
+        return new ArrayAdapter<>(context, androidx.appcompat.R.layout.support_simple_spinner_dropdown_item);
     }
 
     public interface ViewProcessor<V> {
@@ -366,4 +366,4 @@ public final class App {
     public static int toPixels(@Nonnull View view, float dps) {
         return toPixels(view.getContext(), dps);
     }
-}
+}

app/src/main/java/org/solovyev/android/calculator/AppModule.java

@@ -7,12 +7,12 @@ import android.graphics.Typeface;
 import android.os.Handler;
 import android.os.Looper;
 import android.preference.PreferenceManager;
-import android.support.annotation.NonNull;
+import androidx.annotation.NonNull;
 import android.util.Log;
 
 import com.squareup.otto.Bus;
-import com.squareup.otto.GeneratedHandlerFinder;
 
+import com.squareup.otto.GeneratedHandlerFinder;
 import org.solovyev.android.calculator.language.Languages;
 import org.solovyev.android.calculator.wizard.CalculatorWizards;
 import org.solovyev.android.checkout.Billing;

app/src/main/java/org/solovyev/android/calculator/BaseActivity.java

@@ -10,14 +10,6 @@ import android.app.Activity;
 import android.content.SharedPreferences;
 import android.graphics.Typeface;
 import android.os.Bundle;
-import android.support.annotation.DrawableRes;
-import android.support.annotation.LayoutRes;
-import android.support.annotation.StringRes;
-import android.support.design.widget.AppBarLayout;
-import android.support.design.widget.FloatingActionButton;
-import android.support.v7.app.ActionBar;
-import android.support.v7.app.AppCompatActivity;
-import android.support.v7.widget.Toolbar;
 import android.view.KeyEvent;
 import android.view.MenuItem;
 import android.view.View;
@@ -25,6 +17,14 @@ import android.view.ViewGroup;
 import android.view.Window;
 import android.widget.TextView;
 
+import androidx.annotation.DrawableRes;
+import androidx.annotation.LayoutRes;
+import androidx.annotation.StringRes;
+import androidx.appcompat.app.ActionBar;
+import androidx.appcompat.app.AppCompatActivity;
+import androidx.appcompat.widget.Toolbar;
+import com.google.android.material.appbar.AppBarLayout;
+import com.google.android.material.floatingactionbutton.FloatingActionButton;
 import org.solovyev.android.Check;
 import org.solovyev.android.calculator.ga.Ga;
 import org.solovyev.android.calculator.language.Language;
@@ -36,8 +36,6 @@ import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
 import javax.inject.Inject;
 
-import butterknife.BindView;
-import butterknife.ButterKnife;
 import dagger.Lazy;
 
 public abstract class BaseActivity extends AppCompatActivity implements SharedPreferences.OnSharedPreferenceChangeListener {
@@ -58,13 +56,10 @@ public abstract class BaseActivity extends AppCompatActivity implements SharedPr
     Lazy<Ga> ga;
     @Inject
     Typeface typeface;
-    @BindView(R.id.main)
     ViewGroup mainView;
     @Nullable
-    @BindView(R.id.toolbar)
     Toolbar toolbar;
     @Nullable
-    @BindView(R.id.fab)
     FloatingActionButton fab;
     @Nonnull
     private Preferences.Gui.Theme theme = Preferences.Gui.Theme.material_theme;
@@ -159,12 +154,16 @@ public abstract class BaseActivity extends AppCompatActivity implements SharedPr
 
     private void createView() {
         setContentView(layoutId);
+        View contentView = findViewById(android.R.id.content);
+        mainView = contentView.findViewById(R.id.main);
+        toolbar = contentView.findViewById(R.id.toolbar);
+        fab = contentView.findViewById(R.id.fab);
+        bindViews(contentView);
         // title must be updated as if a non-system language is used the value from AndroidManifest
         // might be cached
         if (titleId != 0) {
             setTitle(titleId);
         }
-        ButterKnife.bind(this, this);
 
         fixFonts(mainView, typeface);
         initToolbar();
@@ -172,6 +171,8 @@ public abstract class BaseActivity extends AppCompatActivity implements SharedPr
         tabs.onCreate();
     }
 
+    protected void bindViews(@Nonnull View contentView) {}
+
     private void initToolbar() {
         if (toolbar == null) {
             return;

app/src/main/java/org/solovyev/android/calculator/BaseDialogFragment.java

@@ -5,19 +5,19 @@ import android.content.DialogInterface;
 import android.content.SharedPreferences;
 import android.graphics.Typeface;
 import android.os.Bundle;
-import android.support.annotation.NonNull;
-import android.support.annotation.Nullable;
-import android.support.annotation.StringRes;
-import android.support.design.widget.TextInputLayout;
-import android.support.v4.app.DialogFragment;
-import android.support.v4.app.FragmentActivity;
-import android.support.v7.app.AlertDialog;
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
 import android.view.LayoutInflater;
 import android.view.View;
 import android.view.inputmethod.InputMethodManager;
 import android.widget.Button;
+import androidx.annotation.StringRes;
+import androidx.appcompat.app.AlertDialog;
+import androidx.fragment.app.DialogFragment;
+import androidx.fragment.app.FragmentActivity;
 import com.google.android.gms.analytics.HitBuilders;
 import com.google.android.gms.analytics.Tracker;
+import com.google.android.material.textfield.TextInputLayout;
 import org.solovyev.android.calculator.ga.Ga;
 
 import javax.inject.Inject;

app/src/main/java/org/solovyev/android/calculator/BaseFragment.java

@@ -3,11 +3,11 @@ package org.solovyev.android.calculator;
 import android.graphics.Typeface;
 import android.os.Bundle;
 import android.os.Parcelable;
-import android.support.annotation.LayoutRes;
-import android.support.annotation.NonNull;
-import android.support.annotation.StringRes;
-import android.support.v4.app.Fragment;
+import androidx.annotation.LayoutRes;
+import androidx.annotation.NonNull;
 import android.view.*;
+import androidx.annotation.StringRes;
+import androidx.fragment.app.Fragment;
 import org.solovyev.android.calculator.ads.AdUi;
 import org.solovyev.android.plotter.Check;
 

app/src/main/java/org/solovyev/android/calculator/Calculator.java

@@ -23,8 +23,8 @@
 package org.solovyev.android.calculator;
 
 import android.content.SharedPreferences;
-import android.support.annotation.NonNull;
-import android.support.annotation.VisibleForTesting;
+import androidx.annotation.NonNull;
+import androidx.annotation.VisibleForTesting;
 import android.text.TextUtils;
 import android.util.Log;
 

app/src/main/java/org/solovyev/android/calculator/CalculatorActivity.java

@@ -25,11 +25,9 @@ package org.solovyev.android.calculator;
 import android.content.SharedPreferences;
 import android.graphics.Typeface;
 import android.os.Bundle;
-import android.support.annotation.StringRes;
-import android.support.v4.app.FragmentManager;
-import android.support.v4.app.FragmentTransaction;
-import android.support.v4.view.GravityCompat;
-import android.support.v7.widget.PopupMenu;
+import androidx.annotation.StringRes;
+import androidx.appcompat.widget.PopupMenu;
+import androidx.core.view.GravityCompat;
 import android.text.SpannableString;
 import android.text.Spanned;
 import android.text.style.StyleSpan;
@@ -38,10 +36,12 @@ import android.view.Menu;
 import android.view.MenuItem;
 import android.view.View;
 import android.widget.FrameLayout;
-import butterknife.BindView;
+import androidx.fragment.app.FragmentManager;
+import androidx.fragment.app.FragmentTransaction;
 import jscl.AngleUnit;
 import jscl.NumeralBase;
 import org.solovyev.android.calculator.converter.ConverterFragment;
+import org.solovyev.android.calculator.databinding.ActivityMainBinding;
 import org.solovyev.android.calculator.history.History;
 import org.solovyev.android.calculator.keyboard.PartialKeyboardUi;
 import org.solovyev.android.widget.menu.CustomPopupMenu;
@@ -65,11 +65,8 @@ public class CalculatorActivity extends BaseActivity implements View.OnClickList
     @Inject
     StartupHelper startupHelper;
     @Nullable
-    @BindView(R.id.partial_keyboard)
     View partialKeyboard;
-    @BindView(R.id.editor)
     FrameLayout editor;
-    @BindView(R.id.main_menu)
     View mainMenuButton;
     private boolean useBackAsPrevious;
 
@@ -77,6 +74,14 @@ public class CalculatorActivity extends BaseActivity implements View.OnClickList
         super(R.layout.activity_main, R.string.cpp_app_name);
     }
 
+    @Override
+    protected void bindViews(@Nonnull View contentView) {
+        ActivityMainBinding binding = ActivityMainBinding.bind(contentView.findViewById(R.id.main));
+        partialKeyboard = binding.partialKeyboard;
+        editor = binding.editorContainer.editor;
+        mainMenuButton = binding.editorContainer.mainMenu;
+    }
+
     @Override
     public void onCreate(@Nullable Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
@@ -149,10 +154,8 @@ public class CalculatorActivity extends BaseActivity implements View.OnClickList
 
     @Override
     public void onClick(View v) {
-        switch (v.getId()) {
-            case R.id.main_menu:
-                mainMenu.toggle();
-                break;
+        if (v.getId() == R.id.main_menu) {
+            mainMenu.toggle();
         }
     }
 
@@ -171,7 +174,7 @@ public class CalculatorActivity extends BaseActivity implements View.OnClickList
 
         public void toggle() {
             if (popup == null) {
-                popup = new CustomPopupMenu(CalculatorActivity.this, mainMenuButton, GravityCompat.END, R.attr.actionOverflowMenuStyle, 0);
+                popup = new CustomPopupMenu(CalculatorActivity.this, mainMenuButton, GravityCompat.END, android.R.attr.actionOverflowMenuStyle, 0);
                 popup.inflate(R.menu.main);
                 popup.setOnMenuItemClickListener(this);
                 popup.setKeepOnSubMenu(true);
@@ -227,45 +230,45 @@ public class CalculatorActivity extends BaseActivity implements View.OnClickList
 
         @Override
         public boolean onMenuItemClick(MenuItem item) {
-            switch (item.getItemId()) {
-                case R.id.menu_settings:
-                    launcher.showSettings();
-                    return true;
-                case R.id.menu_history:
-                    launcher.showHistory();
-                    return true;
-                case R.id.menu_plotter:
-                    launcher.showPlotter();
-                    return true;
-                case R.id.menu_conversion_tool:
-                    ConverterFragment.show(CalculatorActivity.this);
-                    return true;
-                case R.id.menu_about:
-                    launcher.showAbout();
-                    return true;
-                case R.id.menu_mode_engineer:
-                    Preferences.Gui.mode.putPreference(preferences, Preferences.Gui.Mode.engineer);
-                    restartIfModeChanged();
-                    return true;
-                case R.id.menu_mode_simple:
-                    Preferences.Gui.mode.putPreference(preferences, Preferences.Gui.Mode.simple);
-                    restartIfModeChanged();
-                    return true;
-                case R.id.menu_au_deg:
-                    Engine.Preferences.angleUnit.putPreference(preferences, AngleUnit.deg);
-                    return true;
-                case R.id.menu_au_rad:
-                    Engine.Preferences.angleUnit.putPreference(preferences, AngleUnit.rad);
-                    return true;
-                case R.id.menu_nb_bin:
-                    Engine.Preferences.numeralBase.putPreference(preferences, NumeralBase.bin);
-                    return true;
-                case R.id.menu_nb_dec:
-                    Engine.Preferences.numeralBase.putPreference(preferences, NumeralBase.dec);
-                    return true;
-                case R.id.menu_nb_hex:
-                    Engine.Preferences.numeralBase.putPreference(preferences, NumeralBase.hex);
-                    return true;
+            int itemId = item.getItemId();
+            if (itemId == R.id.menu_settings) {
+                launcher.showSettings();
+                return true;
+            } else if (itemId == R.id.menu_history) {
+                launcher.showHistory();
+                return true;
+            } else if (itemId == R.id.menu_plotter) {
+                launcher.showPlotter();
+                return true;
+            } else if (itemId == R.id.menu_conversion_tool) {
+                ConverterFragment.show(CalculatorActivity.this);
+                return true;
+            } else if (itemId == R.id.menu_about) {
+                launcher.showAbout();
+                return true;
+            } else if (itemId == R.id.menu_mode_engineer) {
+                Preferences.Gui.mode.putPreference(preferences, Preferences.Gui.Mode.engineer);
+                restartIfModeChanged();
+                return true;
+            } else if (itemId == R.id.menu_mode_simple) {
+                Preferences.Gui.mode.putPreference(preferences, Preferences.Gui.Mode.simple);
+                restartIfModeChanged();
+                return true;
+            } else if (itemId == R.id.menu_au_deg) {
+                Engine.Preferences.angleUnit.putPreference(preferences, AngleUnit.deg);
+                return true;
+            } else if (itemId == R.id.menu_au_rad) {
+                Engine.Preferences.angleUnit.putPreference(preferences, AngleUnit.rad);
+                return true;
+            } else if (itemId == R.id.menu_nb_bin) {
+                Engine.Preferences.numeralBase.putPreference(preferences, NumeralBase.bin);
+                return true;
+            } else if (itemId == R.id.menu_nb_dec) {
+                Engine.Preferences.numeralBase.putPreference(preferences, NumeralBase.dec);
+                return true;
+            } else if (itemId == R.id.menu_nb_hex) {
+                Engine.Preferences.numeralBase.putPreference(preferences, NumeralBase.hex);
+                return true;
             }
             return false;
         }
@@ -280,4 +283,4 @@ public class CalculatorActivity extends BaseActivity implements View.OnClickList
             }
         }
     }
-}
+}

app/src/main/java/org/solovyev/android/calculator/CalculatorApplication.java

@@ -26,7 +26,7 @@ import android.content.SharedPreferences;
 import android.os.AsyncTask;
 import android.os.Handler;
 import android.preference.PreferenceManager;
-import android.support.annotation.NonNull;
+import androidx.annotation.NonNull;
 import android.util.Log;
 import android.util.TimingLogger;
 

app/src/main/java/org/solovyev/android/calculator/Clipboard.java

@@ -23,8 +23,9 @@
 package org.solovyev.android.calculator;
 
 import android.app.Application;
+import android.content.ClipData;
+import android.content.ClipboardManager;
 import android.content.Context;
-import android.text.ClipboardManager;
 
 import javax.annotation.Nonnull;
 import javax.inject.Inject;
@@ -32,31 +33,30 @@ import javax.inject.Singleton;
 
 @Singleton
 public class Clipboard {
-    @SuppressWarnings("deprecation")
     @Nonnull
     private final ClipboardManager clipboard;
 
-    @SuppressWarnings("deprecation")
     @Inject
     public Clipboard(@Nonnull Application application) {
         clipboard = (ClipboardManager) application.getSystemService(Context.CLIPBOARD_SERVICE);
     }
 
-    @SuppressWarnings("deprecation")
     @Nonnull
     public String getText() {
-        if (clipboard.hasText()) {
-            return String.valueOf(clipboard.getText());
+        ClipData primaryClip = clipboard.getPrimaryClip();
+        if (primaryClip != null && primaryClip.getItemCount() > 0) {
+            final CharSequence text = primaryClip.getItemAt(0).getText();
+            return text != null ? text.toString() : "";
         }
 
         return "";
     }
 
     public void setText(@Nonnull CharSequence text) {
-        clipboard.setText(text);
+        clipboard.setPrimaryClip(ClipData.newPlainText("", text));
     }
 
     public void setText(@Nonnull String text) {
-        clipboard.setText(text);
+        setText((CharSequence) text);
     }
 }

app/src/main/java/org/solovyev/android/calculator/Display.java

@@ -24,7 +24,7 @@ package org.solovyev.android.calculator;
 
 import android.app.Application;
 import android.content.Context;
-import android.support.annotation.NonNull;
+import androidx.annotation.NonNull;
 
 import com.squareup.otto.Bus;
 import com.squareup.otto.Subscribe;

app/src/main/java/org/solovyev/android/calculator/DisplayFragment.java

@@ -25,14 +25,12 @@ package org.solovyev.android.calculator;
 import android.content.Context;
 import android.content.SharedPreferences;
 import android.os.Bundle;
-import android.support.annotation.NonNull;
-import android.support.annotation.Nullable;
-import android.support.annotation.StringRes;
-import android.support.v7.app.AlertDialog;
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import androidx.annotation.StringRes;
 import android.view.*;
 
-import butterknife.BindView;
-import butterknife.ButterKnife;
+import androidx.appcompat.app.AlertDialog;
 import com.squareup.otto.Bus;
 import jscl.NumeralBase;
 import jscl.math.Generic;
@@ -63,19 +61,17 @@ public class DisplayFragment extends BaseFragment implements View.OnClickListene
 
         @Nullable
         public static ConversionMenuItem getByTitle(int title) {
-            switch (title) {
-                case R.string.convert_to_bin:
-                    return to_bin;
-                case R.string.convert_to_dec:
-                    return to_dec;
-                case R.string.convert_to_hex:
-                    return to_hex;
+            if (title == R.string.convert_to_bin) {
+                return to_bin;
+            } else if (title == R.string.convert_to_dec) {
+                return to_dec;
+            } else if (title == R.string.convert_to_hex) {
+                return to_hex;
             }
             return null;
         }
     }
 
-    @BindView(R.id.calculator_display)
     DisplayView displayView;
     @Inject
     SharedPreferences preferences;
@@ -106,7 +102,7 @@ public class DisplayFragment extends BaseFragment implements View.OnClickListene
     public View onCreateView(LayoutInflater inflater, ViewGroup container,
             Bundle savedInstanceState) {
         final View view = super.onCreateView(inflater, container, savedInstanceState);
-        ButterKnife.bind(this, view);
+        displayView = view.findViewById(R.id.calculator_display);
         display.setView(displayView);
         displayView.setOnClickListener(this);
         return view;
@@ -181,30 +177,27 @@ public class DisplayFragment extends BaseFragment implements View.OnClickListene
     public boolean onMenuItemClick(MenuItem item) {
         final DisplayState state = display.getState();
         final Generic result = state.getResult();
-        switch (item.getItemId()) {
-            case R.string.cpp_copy:
-                display.copy();
-                return true;
-            case R.string.convert_to_bin:
-            case R.string.convert_to_dec:
-            case R.string.convert_to_hex:
-                final ConversionMenuItem menuItem = ConversionMenuItem.getByTitle(item.getItemId());
-                if (menuItem == null) {
-                    return false;
-                }
-                if (result != null) {
-                    calculator.convert(state, menuItem.toNumeralBase);
-                }
-                return true;
-            case R.string.c_convert:
-                ConverterFragment.show(getActivity(), getValue(result));
-                return true;
-            case R.string.c_plot:
-                launcher.plot(result);
-                return true;
-            default:
+        int itemId = item.getItemId();
+        if (itemId == R.string.cpp_copy) {
+            display.copy();
+            return true;
+        } else if (itemId == R.string.convert_to_bin || itemId == R.string.convert_to_dec || itemId == R.string.convert_to_hex) {
+            final ConversionMenuItem menuItem = ConversionMenuItem.getByTitle(item.getItemId());
+            if (menuItem == null) {
                 return false;
+            }
+            if (result != null) {
+                calculator.convert(state, menuItem.toNumeralBase);
+            }
+            return true;
+        } else if (itemId == R.string.c_convert) {
+            ConverterFragment.show(getActivity(), getValue(result));
+            return true;
+        } else if (itemId == R.string.c_plot) {
+            launcher.plot(result);
+            return true;
         }
+        return false;
     }
 
     private static double getValue(@Nullable Generic result) {

app/src/main/java/org/solovyev/android/calculator/DisplayView.java

@@ -28,8 +28,8 @@ import static android.util.TypedValue.applyDimension;
 import android.content.Context;
 import android.content.res.Resources;
 import android.os.AsyncTask;
-import android.support.annotation.NonNull;
-import android.support.annotation.Nullable;
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
 import android.text.TextUtils;
 import android.text.method.ScrollingMovementMethod;
 import android.util.AttributeSet;

app/src/main/java/org/solovyev/android/calculator/Editor.java

@@ -27,8 +27,8 @@ import static java.lang.Math.min;
 import android.app.Application;
 import android.content.SharedPreferences;
 import android.os.AsyncTask;
-import android.support.annotation.NonNull;
-import android.support.annotation.VisibleForTesting;
+import androidx.annotation.NonNull;
+import androidx.annotation.VisibleForTesting;
 import android.text.TextUtils;
 
 import com.squareup.otto.Bus;
@@ -173,12 +173,13 @@ public class Editor {
         state = newState;
 
         cancelAsyncHighlightText();
-        highlighterTask = new AsyncHighlighter(oldState, newState, force, textProcessor);
-        if (highlighterTask.shouldAsync()) {
-            highlighterTask.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
+        AsyncHighlighter newHighlighterTask = new AsyncHighlighter(oldState, newState, force, textProcessor);
+        highlighterTask = newHighlighterTask;
+        if (newHighlighterTask.shouldAsync()) {
+            newHighlighterTask.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
             return;
         }
-        highlighterTask.onPostExecute(newState);
+        newHighlighterTask.onPostExecute(newState);
         Check.isNull(highlighterTask);
     }
 

app/src/main/java/org/solovyev/android/calculator/EditorFragment.java

@@ -26,17 +26,15 @@ import android.os.Bundle;
 import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
-import butterknife.BindView;
-import butterknife.ButterKnife;
 
 import javax.annotation.Nonnull;
 import javax.inject.Inject;
+import org.solovyev.android.calculator.databinding.CppAppEditorBinding;
 
 public class EditorFragment extends BaseFragment {
 
     @Inject
     Editor editor;
-    @BindView(R.id.calculator_editor)
     EditorView editorView;
 
     public EditorFragment() {
@@ -52,7 +50,8 @@ public class EditorFragment extends BaseFragment {
     @Override
     public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
         final View view = super.onCreateView(inflater, container, savedInstanceState);
-        ButterKnife.bind(this, view);
+        CppAppEditorBinding binding = CppAppEditorBinding.bind(view);
+        editorView = binding.calculatorEditor;
         editor.setView(editorView);
         return view;
     }

app/src/main/java/org/solovyev/android/calculator/Engine.java

@@ -24,9 +24,9 @@ package org.solovyev.android.calculator;
 
 import android.content.Context;
 import android.content.SharedPreferences;
-import android.support.annotation.NonNull;
-import android.support.annotation.StringRes;
-import android.support.annotation.VisibleForTesting;
+import androidx.annotation.NonNull;
+import androidx.annotation.StringRes;
+import androidx.annotation.VisibleForTesting;
 import android.text.TextUtils;
 
 import com.squareup.otto.Bus;

app/src/main/java/org/solovyev/android/calculator/FloatingCalculatorKeyboard.java

@@ -1,7 +1,7 @@
 package org.solovyev.android.calculator;
 
-import android.support.annotation.IdRes;
-import android.support.annotation.NonNull;
+import androidx.annotation.IdRes;
+import androidx.annotation.NonNull;
 import android.text.TextUtils;
 import android.view.View;
 import android.widget.Button;
@@ -174,47 +174,34 @@ public class FloatingCalculatorKeyboard extends BaseFloatingKeyboard {
             if (user.isVibrateOnKeypress()) {
                 v.performHapticFeedback(KEYBOARD_TAP, FLAG_IGNORE_GLOBAL_SETTING | FLAG_IGNORE_VIEW_SETTING);
             }
-            switch (v.getId()) {
-                case R.id.cpp_kb_button_divide:
-                    user.insertOperator('/');
-                    break;
-                case R.id.cpp_kb_button_plus:
-                    user.insertOperator('+');
-                    break;
-                case R.id.cpp_kb_button_minus:
-                    user.insertOperator('-');
-                    break;
-                case R.id.cpp_kb_button_multiply:
-                    user.insertOperator("×");
-                    break;
-                case R.id.cpp_kb_button_functions_constants:
-                    user.showFunctionsConstants(v);
-                    break;
-                case R.id.cpp_kb_button_functions:
-                    user.showFunctions(v);
-                    break;
-                case R.id.cpp_kb_button_constants:
-                    user.showConstants(v);
-                    break;
-                case R.id.cpp_kb_button_space:
-                    user.insertText(" ", 0);
-                    break;
-                case R.id.cpp_kb_button_keyboard:
-                    user.showIme();
-                    break;
-                case R.id.cpp_kb_button_clear:
-                    user.getEditor().setText("");
-                    user.getEditor().setSelection(0);
-                    break;
-                case R.id.cpp_kb_button_brackets:
-                    user.insertText("()", -1);
-                    break;
-                case R.id.cpp_kb_button_close:
-                    user.done();
-                    break;
-                default:
-                    onDefaultClick(v);
-                    break;
+            int id = v.getId();
+            if (id == R.id.cpp_kb_button_divide) {
+                user.insertOperator('/');
+            } else if (id == R.id.cpp_kb_button_plus) {
+                user.insertOperator('+');
+            } else if (id == R.id.cpp_kb_button_minus) {
+                user.insertOperator('-');
+            } else if (id == R.id.cpp_kb_button_multiply) {
+                user.insertOperator("×");
+            } else if (id == R.id.cpp_kb_button_functions_constants) {
+                user.showFunctionsConstants(v);
+            } else if (id == R.id.cpp_kb_button_functions) {
+                user.showFunctions(v);
+            } else if (id == R.id.cpp_kb_button_constants) {
+                user.showConstants(v);
+            } else if (id == R.id.cpp_kb_button_space) {
+                user.insertText(" ", 0);
+            } else if (id == R.id.cpp_kb_button_keyboard) {
+                user.showIme();
+            } else if (id == R.id.cpp_kb_button_clear) {
+                user.getEditor().setText("");
+                user.getEditor().setSelection(0);
+            } else if (id == R.id.cpp_kb_button_brackets) {
+                user.insertText("()", -1);
+            } else if (id == R.id.cpp_kb_button_close) {
+                user.done();
+            } else {
+                onDefaultClick(v);
             }
             user.getEditor().requestFocus();
         }
@@ -256,4 +243,4 @@ public class FloatingCalculatorKeyboard extends BaseFloatingKeyboard {
             return true;
         }
     }
-}
+}

app/src/main/java/org/solovyev/android/calculator/FragmentTab.java

@@ -22,8 +22,8 @@
 
 package org.solovyev.android.calculator;
 
-import android.support.annotation.StringRes;
-import android.support.v4.app.Fragment;
+import androidx.annotation.StringRes;
+import androidx.fragment.app.Fragment;
 import org.solovyev.android.calculator.about.AboutFragment;
 import org.solovyev.android.calculator.about.ReleaseNotesFragment;
 import org.solovyev.android.calculator.functions.FunctionsFragment;

app/src/main/java/org/solovyev/android/calculator/Keyboard.java

@@ -25,7 +25,7 @@ package org.solovyev.android.calculator;
 import static org.solovyev.android.calculator.Engine.Preferences.numeralBase;
 
 import android.content.SharedPreferences;
-import android.support.annotation.NonNull;
+import androidx.annotation.NonNull;
 import android.text.Spannable;
 import android.text.TextUtils;
 import android.util.Log;
@@ -366,4 +366,4 @@ public class Keyboard implements SharedPreferences.OnSharedPreferenceChangeListe
             this.mode = mode;
         }
     }
-}
+}

app/src/main/java/org/solovyev/android/calculator/KeyboardFragment.java

@@ -22,12 +22,10 @@
 
 package org.solovyev.android.calculator;
 
-import android.content.SharedPreferences;
 import android.os.Bundle;
 import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
-import butterknife.ButterKnife;
 import org.solovyev.android.Check;
 import org.solovyev.android.calculator.keyboard.KeyboardUi;
 
@@ -36,8 +34,6 @@ import javax.inject.Inject;
 
 public class KeyboardFragment extends BaseFragment {
 
-    @Inject
-    SharedPreferences preferences;
     @Inject
     KeyboardUi keyboardUi;
 
@@ -54,7 +50,6 @@ public class KeyboardFragment extends BaseFragment {
     @Override
     public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
         final View view = super.onCreateView(inflater, container, savedInstanceState);
-        ButterKnife.bind(this, view);
         Check.isNotNull(view);
         keyboardUi.onCreateView(getActivity(), view);
         return view;

app/src/main/java/org/solovyev/android/calculator/Named.java

@@ -1,8 +1,8 @@
 package org.solovyev.android.calculator;
 
 import android.content.Context;
-import android.support.annotation.NonNull;
-import android.support.annotation.StringRes;
+import androidx.annotation.NonNull;
+import androidx.annotation.StringRes;
 
 import javax.annotation.Nonnull;
 

app/src/main/java/org/solovyev/android/calculator/Notifier.java

@@ -24,7 +24,7 @@ package org.solovyev.android.calculator;
 
 import android.app.Application;
 import android.os.Handler;
-import android.support.annotation.StringRes;
+import androidx.annotation.StringRes;
 import android.widget.Toast;
 import org.solovyev.common.msg.Message;
 

app/src/main/java/org/solovyev/android/calculator/Preferences.java

@@ -31,11 +31,11 @@ import android.content.SharedPreferences;
 import android.content.res.TypedArray;
 import android.graphics.Color;
 import android.provider.Settings;
-import android.support.annotation.ColorRes;
-import android.support.annotation.LayoutRes;
-import android.support.annotation.NonNull;
-import android.support.annotation.StringRes;
-import android.support.annotation.StyleRes;
+import androidx.annotation.ColorRes;
+import androidx.annotation.LayoutRes;
+import androidx.annotation.NonNull;
+import androidx.annotation.StringRes;
+import androidx.annotation.StyleRes;
 import android.text.TextUtils;
 import android.util.SparseArray;
 import android.view.ContextThemeWrapper;

app/src/main/java/org/solovyev/android/calculator/PreparedExpression.java

@@ -22,7 +22,7 @@
 
 package org.solovyev.android.calculator;
 
-import android.support.annotation.NonNull;
+import androidx.annotation.NonNull;
 import jscl.math.function.IConstant;
 
 import javax.annotation.Nonnull;

app/src/main/java/org/solovyev/android/calculator/RemovalConfirmationDialog.java

@@ -2,9 +2,9 @@ package org.solovyev.android.calculator;
 
 import android.app.Activity;
 import android.content.DialogInterface;
-import android.support.annotation.StringRes;
-import android.support.v7.app.AlertDialog;
+import androidx.annotation.StringRes;
 
+import androidx.appcompat.app.AlertDialog;
 import javax.annotation.Nonnull;
 
 public class RemovalConfirmationDialog {

app/src/main/java/org/solovyev/android/calculator/Runnables.java

@@ -1,6 +1,6 @@
 package org.solovyev.android.calculator;
 
-import android.support.annotation.NonNull;
+import androidx.annotation.NonNull;
 import org.solovyev.android.Check;
 
 import java.util.ArrayList;

app/src/main/java/org/solovyev/android/calculator/StartupHelper.java

@@ -6,9 +6,9 @@ import android.content.Intent;
 import android.content.SharedPreferences;
 import android.net.Uri;
 import android.os.Bundle;
-import android.support.annotation.NonNull;
-import android.support.v7.app.AlertDialog;
-import android.support.v7.app.AppCompatActivity;
+import androidx.annotation.NonNull;
+import androidx.appcompat.app.AlertDialog;
+import androidx.appcompat.app.AppCompatActivity;
 import org.solovyev.android.calculator.wizard.CalculatorWizards;
 import org.solovyev.android.wizard.Wizard;
 import org.solovyev.android.wizard.Wizards;

app/src/main/java/org/solovyev/android/calculator/TaskExecutor.java

@@ -1,7 +1,7 @@
 package org.solovyev.android.calculator;
 
-import android.support.annotation.NonNull;
-import android.support.annotation.VisibleForTesting;
+import androidx.annotation.NonNull;
+import androidx.annotation.VisibleForTesting;
 import android.util.Log;
 
 import org.solovyev.android.Check;
@@ -118,4 +118,4 @@ class TaskExecutor {
     void setSynchronous() {
         synchronous = true;
     }
-}
+}

app/src/main/java/org/solovyev/android/calculator/ToJsclTextProcessor.java

@@ -41,7 +41,7 @@ public class ToJsclTextProcessor implements TextProcessor<PreparedExpression, St
 
     @Nonnull
     private static final Integer MAX_DEPTH = 20;
-    
+
     @Inject
     Engine engine;
 
@@ -50,7 +50,17 @@ public class ToJsclTextProcessor implements TextProcessor<PreparedExpression, St
     }
 
     private static PreparedExpression processWithDepth(@Nonnull String s, int depth, @Nonnull List<IConstant> undefinedVars, @Nonnull Engine engine) throws ParseException {
-        return replaceVariables(processExpression(s, engine).toString(), depth, undefinedVars, engine);
+        return replaceVariables(processExpression(removeWhitespaces(s), engine).toString(), depth, undefinedVars, engine);
+    }
+
+    private static String removeWhitespaces(String s) {
+        final StringBuilder res = new StringBuilder(s.length());
+        for (int i = 0; i < s.length(); i++) {
+            char c = s.charAt(i);
+            if (Character.isWhitespace(c)) continue;
+            res.append(c);
+        }
+        return res.toString();
     }
 
     @Nonnull

app/src/main/java/org/solovyev/android/calculator/UiPreferences.java

@@ -1,7 +1,7 @@
 package org.solovyev.android.calculator;
 
 import android.content.SharedPreferences;
-import android.support.annotation.NonNull;
+import androidx.annotation.NonNull;
 
 import org.solovyev.android.prefs.BooleanPreference;
 import org.solovyev.android.prefs.IntegerPreference;

app/src/main/java/org/solovyev/android/calculator/VariablesRegistry.java

@@ -22,7 +22,7 @@
 
 package org.solovyev.android.calculator;
 
-import android.support.annotation.NonNull;
+import androidx.annotation.NonNull;
 
 import com.google.common.base.Strings;
 

app/src/main/java/org/solovyev/android/calculator/WidgetReceiver.java

@@ -4,7 +4,7 @@ import android.content.BroadcastReceiver;
 import android.content.Context;
 import android.content.Intent;
 import android.os.Vibrator;
-import android.support.annotation.NonNull;
+import androidx.annotation.NonNull;
 import android.text.TextUtils;
 
 import org.solovyev.android.calculator.buttons.CppButton;
@@ -40,7 +40,9 @@ public final class WidgetReceiver extends BroadcastReceiver {
             return;
         }
 
-        cast(context).getComponent().inject(this);
+        if (keyboard == null || history == null) {
+            cast(context).getComponent().inject(this);
+        }
 
         final int buttonId = intent.getIntExtra(ACTION_BUTTON_ID_EXTRA, 0);
         final CppButton button = CppButton.getById(buttonId);

app/src/main/java/org/solovyev/android/calculator/about/AboutActivity.java

@@ -23,7 +23,7 @@
 package org.solovyev.android.calculator.about;
 
 import android.content.Context;
-import android.support.annotation.NonNull;
+import androidx.annotation.NonNull;
 
 import org.solovyev.android.calculator.App;
 import org.solovyev.android.calculator.BaseActivity;

app/src/main/java/org/solovyev/android/calculator/about/AboutFragment.java

@@ -29,24 +29,19 @@ import android.view.View;
 import android.view.ViewGroup;
 import android.widget.ImageView;
 import android.widget.TextView;
-import butterknife.BindView;
-import butterknife.ButterKnife;
 import org.solovyev.android.calculator.App;
 import org.solovyev.android.calculator.BaseFragment;
 import org.solovyev.android.calculator.R;
+import org.solovyev.android.calculator.databinding.FragmentAboutBinding;
 
 import static android.view.View.GONE;
 import static org.solovyev.common.text.Strings.isEmpty;
 
 public class AboutFragment extends BaseFragment {
 
-    @BindView(R.id.about_image)
     ImageView imageView;
-    @BindView(R.id.about_text)
     TextView textView;
-    @BindView(R.id.about_translators_label)
     TextView translatorsLabel;
-    @BindView(R.id.about_translators)
     TextView translatorsView;
 
     public AboutFragment() {
@@ -56,7 +51,11 @@ public class AboutFragment extends BaseFragment {
     @Override
     public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
         final View view = super.onCreateView(inflater, container, savedInstanceState);
-        ButterKnife.bind(this, view);
+        final FragmentAboutBinding binding = FragmentAboutBinding.bind(view);
+        imageView = binding.aboutImage;
+        textView = binding.aboutText;
+        translatorsLabel = binding.aboutTranslatorsLabel;
+        translatorsView = binding.aboutTranslators;
         if (App.getTheme().light) {
             imageView.setImageResource(R.drawable.logo_wizard_light);
         }

app/src/main/java/org/solovyev/android/calculator/about/ReleaseNotesFragment.java

@@ -29,15 +29,13 @@ import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
 import android.widget.TextView;
-import butterknife.BindView;
-import butterknife.ButterKnife;
 import org.solovyev.android.calculator.BaseFragment;
 import org.solovyev.android.calculator.R;
+import org.solovyev.android.calculator.databinding.FragmentReleaseNotesBinding;
 import org.solovyev.android.calculator.release.ReleaseNotes;
 
 public class ReleaseNotesFragment extends BaseFragment {
 
-    @BindView(R.id.releasenotes_text)
     TextView text;
 
     public ReleaseNotesFragment() {
@@ -47,7 +45,8 @@ public class ReleaseNotesFragment extends BaseFragment {
     @Override
     public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
         final View view = super.onCreateView(inflater, container, savedInstanceState);
-        ButterKnife.bind(this, view);
+        final FragmentReleaseNotesBinding binding = FragmentReleaseNotesBinding.bind(view);
+        text = binding.releasenotesText;
         text.setMovementMethod(LinkMovementMethod.getInstance());
         text.setText(Html.fromHtml(ReleaseNotes.getReleaseNotes(getActivity())));
         return view;

app/src/main/java/org/solovyev/android/calculator/ads/AdUi.java

@@ -4,7 +4,7 @@ import static org.solovyev.android.checkout.ProductTypes.IN_APP;
 
 import android.os.Handler;
 import android.os.Looper;
-import android.support.annotation.NonNull;
+import androidx.annotation.NonNull;
 import android.view.View;
 
 import org.solovyev.android.calculator.AdView;
@@ -16,8 +16,6 @@ import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
 import javax.inject.Inject;
 
-import butterknife.BindView;
-import butterknife.ButterKnife;
 
 public class AdUi {
 
@@ -26,7 +24,6 @@ public class AdUi {
     @NonNull
     private final Handler handler;
     @Nullable
-    @BindView(R.id.cpp_ad)
     AdView adView;
     @Nullable
     private Boolean adFree = null;
@@ -92,7 +89,7 @@ public class AdUi {
     }
 
     public void onCreateView(@NonNull View view) {
-        ButterKnife.bind(this, view);
+        adView = view.findViewById(R.id.cpp_ad);
     }
 
     public void onPause() {

app/src/main/java/org/solovyev/android/calculator/calculations/BaseConversionEvent.java

@@ -1,6 +1,6 @@
 package org.solovyev.android.calculator.calculations;
 
-import android.support.annotation.NonNull;
+import androidx.annotation.NonNull;
 
 import org.solovyev.android.calculator.DisplayState;
 

app/src/main/java/org/solovyev/android/calculator/calculations/ConversionFailedEvent.java

@@ -1,6 +1,6 @@
 package org.solovyev.android.calculator.calculations;
 
-import android.support.annotation.NonNull;
+import androidx.annotation.NonNull;
 
 import org.solovyev.android.calculator.DisplayState;
 

app/src/main/java/org/solovyev/android/calculator/calculations/ConversionFinishedEvent.java

@@ -1,6 +1,6 @@
 package org.solovyev.android.calculator.calculations;
 
-import android.support.annotation.NonNull;
+import androidx.annotation.NonNull;
 
 import org.solovyev.android.calculator.DisplayState;
 

app/src/main/java/org/solovyev/android/calculator/converter/Converter.java

@@ -1,14 +1,14 @@
 package org.solovyev.android.calculator.converter;
 
-import android.support.annotation.NonNull;
+import androidx.annotation.NonNull;
 import android.util.Log;
 import com.google.common.base.Strings;
+import javax.measure.unit.Unit;
 import jscl.JsclMathEngine;
 import midpcalc.Real;
 import org.solovyev.android.calculator.R;
 
 import javax.annotation.Nonnull;
-import javax.measure.unit.Unit;
 
 final class Converter {
     static int unitName(@Nonnull Unit unit, @Nonnull UnitDimension dimension) {

app/src/main/java/org/solovyev/android/calculator/converter/ConverterFragment.java

@@ -6,11 +6,8 @@ import android.content.DialogInterface;
 import android.content.SharedPreferences;
 import android.graphics.Typeface;
 import android.os.Bundle;
-import android.support.annotation.NonNull;
-import android.support.annotation.Nullable;
-import android.support.design.widget.TextInputLayout;
-import android.support.v4.app.FragmentActivity;
-import android.support.v7.app.AlertDialog;
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
 import android.text.Editable;
 import android.text.InputType;
 import android.text.TextUtils;
@@ -29,6 +26,9 @@ import android.widget.Spinner;
 import android.widget.TextView;
 import android.widget.Toast;
 
+import androidx.appcompat.app.AlertDialog;
+import androidx.fragment.app.FragmentActivity;
+import com.google.android.material.textfield.TextInputLayout;
 import org.solovyev.android.calculator.App;
 import org.solovyev.android.calculator.AppComponent;
 import org.solovyev.android.calculator.AppModule;
@@ -38,6 +38,7 @@ import org.solovyev.android.calculator.Editor;
 import org.solovyev.android.calculator.Keyboard;
 import org.solovyev.android.calculator.Named;
 import org.solovyev.android.calculator.R;
+import org.solovyev.android.calculator.databinding.CppUnitConverterBinding;
 import org.solovyev.android.calculator.keyboard.FloatingKeyboard;
 import org.solovyev.android.calculator.keyboard.FloatingKeyboardWindow;
 import org.solovyev.android.calculator.keyboard.FloatingNumberKeyboard;
@@ -48,9 +49,6 @@ import org.solovyev.android.calculator.view.EditTextCompat;
 import javax.annotation.Nonnull;
 import javax.inject.Inject;
 
-import butterknife.BindView;
-import butterknife.ButterKnife;
-
 import static org.solovyev.android.calculator.UiPreferences.Converter.lastDimension;
 import static org.solovyev.android.calculator.UiPreferences.Converter.lastUnitsFrom;
 import static org.solovyev.android.calculator.UiPreferences.Converter.lastUnitsTo;
@@ -77,21 +75,13 @@ public class ConverterFragment extends BaseDialogFragment
     SharedPreferences uiPreferences;
     @Inject
     Editor editor;
-    @BindView(R.id.converter_dimensions_spinner)
     Spinner dimensionsSpinner;
-    @BindView(R.id.converter_spinner_from)
     Spinner spinnerFrom;
-    @BindView(R.id.converter_label_from)
     TextInputLayout labelFrom;
-    @BindView(R.id.converter_edittext_from)
     EditTextCompat editTextFrom;
-    @BindView(R.id.converter_spinner_to)
     Spinner spinnerTo;
-    @BindView(R.id.converter_label_to)
     TextInputLayout labelTo;
-    @BindView(R.id.converter_edittext_to)
     EditText editTextTo;
-    @BindView(R.id.converter_swap_button)
     ImageButton swapButton;
     private ArrayAdapter<Named<ConvertibleDimension>> dimensionsAdapter;
     private ArrayAdapter<Named<Convertible>> adapterFrom;
@@ -139,9 +129,15 @@ public class ConverterFragment extends BaseDialogFragment
     @Override
     protected View onCreateDialogView(@NonNull Context context, @NonNull LayoutInflater inflater,
                                       @Nullable Bundle savedInstanceState) {
-        final View view = inflater.inflate(R.layout.cpp_unit_converter, null);
-        ButterKnife.bind(this, view);
-
+        final CppUnitConverterBinding binding = CppUnitConverterBinding.inflate(inflater, null, false);
+        dimensionsSpinner = binding.converterDimensionsSpinner;
+        spinnerFrom = binding.converterSpinnerFrom;
+        labelFrom = binding.converterLabelFrom;
+        editTextFrom = binding.converterEdittextFrom;
+        spinnerTo = binding.converterSpinnerTo;
+        labelTo = binding.converterLabelTo;
+        editTextTo = binding.converterEdittextTo;
+        swapButton = binding.converterSwapButton;
         dimensionsAdapter = App.makeSimpleSpinnerAdapter(context);
         for (ConvertibleDimension dimension : UnitDimension.values()) {
             dimensionsAdapter.add(dimension.named(context));
@@ -177,7 +173,7 @@ public class ConverterFragment extends BaseDialogFragment
             pendingToSelection = savedInstanceState.getInt(STATE_SELECTION_TO, NONE);
         }
 
-        return view;
+        return binding.getRoot();
     }
 
     @Override
@@ -203,16 +199,13 @@ public class ConverterFragment extends BaseDialogFragment
 
     @Override
     public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
-        switch (parent.getId()) {
-            case R.id.converter_dimensions_spinner:
-                onDimensionChanged(dimensionsAdapter.getItem(position).item);
-                break;
-            case R.id.converter_spinner_from:
-                onUnitFromChanged(adapterFrom.getItem(position).item);
-                break;
-            case R.id.converter_spinner_to:
-                convert();
-                break;
+        int parentId = parent.getId();
+        if (parentId == R.id.converter_dimensions_spinner) {
+            onDimensionChanged(dimensionsAdapter.getItem(position).item);
+        } else if (parentId == R.id.converter_spinner_from) {
+            onUnitFromChanged(adapterFrom.getItem(position).item);
+        } else if (parentId == R.id.converter_spinner_to) {
+            convert();
         }
     }
 
@@ -299,15 +292,13 @@ public class ConverterFragment extends BaseDialogFragment
 
     @Override
     public void onFocusChange(View v, boolean hasFocus) {
-        switch (v.getId()) {
-            case R.id.converter_edittext_from:
-                if (!hasFocus) {
-                    convert();
-                } else {
-                    clearError(labelFrom);
-                    showKeyboard();
-                }
-                break;
+        if (v.getId() == R.id.converter_edittext_from) {
+            if (!hasFocus) {
+                convert();
+            } else {
+                clearError(labelFrom);
+                showKeyboard();
+            }
         }
     }
 
@@ -346,31 +337,26 @@ public class ConverterFragment extends BaseDialogFragment
 
     @Override
     public boolean onEditorAction(TextView v, int actionId, KeyEvent event) {
-        switch (v.getId()) {
-            case R.id.converter_edittext_from:
-                if (actionId == EditorInfo.IME_ACTION_DONE) {
-                    App.hideIme(editTextFrom);
-                    convert();
-                    return true;
-                }
-                break;
+        if (v.getId() == R.id.converter_edittext_from) {
+            if (actionId == EditorInfo.IME_ACTION_DONE) {
+                App.hideIme(editTextFrom);
+                convert();
+                return true;
+            }
         }
         return false;
     }
 
     @Override
     public void onClick(View v) {
-        switch (v.getId()) {
-            case R.id.converter_swap_button:
-                keyboardWindow.hide();
-                swap();
-                break;
-            case R.id.converter_edittext_from:
-                showKeyboard();
-                break;
-            default:
-                super.onClick(v);
-                break;
+        int id = v.getId();
+        if (id == R.id.converter_swap_button) {
+            keyboardWindow.hide();
+            swap();
+        } else if (id == R.id.converter_edittext_from) {
+            showKeyboard();
+        } else {
+            super.onClick(v);
         }
     }
 

app/src/main/java/org/solovyev/android/calculator/converter/Convertible.java

@@ -1,7 +1,7 @@
 package org.solovyev.android.calculator.converter;
 
 import android.content.Context;
-import android.support.annotation.NonNull;
+import androidx.annotation.NonNull;
 
 import org.solovyev.android.calculator.Named;
 

app/src/main/java/org/solovyev/android/calculator/converter/ConvertibleDimension.java

@@ -1,7 +1,7 @@
 package org.solovyev.android.calculator.converter;
 
 import android.content.Context;
-import android.support.annotation.NonNull;
+import androidx.annotation.NonNull;
 
 import org.solovyev.android.calculator.Named;
 

app/src/main/java/org/solovyev/android/calculator/converter/NumeralBaseConvertible.java

@@ -1,7 +1,7 @@
 package org.solovyev.android.calculator.converter;
 
 import android.content.Context;
-import android.support.annotation.NonNull;
+import androidx.annotation.NonNull;
 
 import org.solovyev.android.calculator.Named;
 

app/src/main/java/org/solovyev/android/calculator/converter/NumeralBaseDimension.java

@@ -1,7 +1,7 @@
 package org.solovyev.android.calculator.converter;
 
 import android.content.Context;
-import android.support.annotation.NonNull;
+import androidx.annotation.NonNull;
 import jscl.NumeralBase;
 
 import org.solovyev.android.calculator.Named;

app/src/main/java/org/solovyev/android/calculator/converter/UnitConvertible.java

@@ -1,15 +1,15 @@
 package org.solovyev.android.calculator.converter;
 
 import android.content.Context;
-import android.support.annotation.NonNull;
+import androidx.annotation.NonNull;
 
+import javax.measure.unit.Unit;
 import org.solovyev.android.calculator.Named;
 
 import jscl.JsclMathEngine;
 import jscl.NumeralBase;
 
 import javax.annotation.Nonnull;
-import javax.measure.unit.Unit;
 
 final class UnitConvertible implements Convertible {
     @NonNull

app/src/main/java/org/solovyev/android/calculator/converter/UnitDimension.java

@@ -1,9 +1,9 @@
 package org.solovyev.android.calculator.converter;
 
 import android.content.Context;
-import android.support.annotation.NonNull;
-import android.support.annotation.Nullable;
-import android.support.annotation.StringRes;
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import androidx.annotation.StringRes;
 
 import org.solovyev.android.calculator.Named;
 import org.solovyev.android.calculator.R;

app/src/main/java/org/solovyev/android/calculator/entities/BaseEntitiesFragment.java

@@ -25,11 +25,11 @@ package org.solovyev.android.calculator.entities;
 import android.app.Activity;
 import android.content.Context;
 import android.os.Bundle;
-import android.support.annotation.NonNull;
-import android.support.v4.app.FragmentActivity;
-import android.support.v7.widget.DividerItemDecoration;
-import android.support.v7.widget.LinearLayoutManager;
-import android.support.v7.widget.RecyclerView;
+import androidx.annotation.NonNull;
+import androidx.fragment.app.FragmentActivity;
+import androidx.recyclerview.widget.DividerItemDecoration;
+import androidx.recyclerview.widget.LinearLayoutManager;
+import androidx.recyclerview.widget.RecyclerView;
 import android.text.ClipboardManager;
 import android.text.TextUtils;
 import android.view.ContextMenu;
@@ -45,6 +45,8 @@ import org.solovyev.android.calculator.BaseFragment;
 import org.solovyev.android.calculator.CalculatorActivity;
 import org.solovyev.android.calculator.Keyboard;
 import org.solovyev.android.calculator.R;
+import org.solovyev.android.calculator.databinding.FragmentEntitiesBinding;
+import org.solovyev.android.calculator.databinding.FragmentEntitiesItemBinding;
 import org.solovyev.common.math.MathEntity;
 import org.solovyev.common.text.Strings;
 
@@ -57,8 +59,6 @@ import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
 import javax.inject.Inject;
 
-import butterknife.BindView;
-import butterknife.ButterKnife;
 
 
 public abstract class BaseEntitiesFragment<E extends MathEntity> extends BaseFragment {
@@ -71,7 +71,6 @@ public abstract class BaseEntitiesFragment<E extends MathEntity> extends BaseFra
         }
     };
 
-    @BindView(R.id.entities_recyclerview)
     public RecyclerView recyclerView;
     @Inject
     Keyboard keyboard;
@@ -96,7 +95,8 @@ public abstract class BaseEntitiesFragment<E extends MathEntity> extends BaseFra
     @Override
     public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
         final View view = super.onCreateView(inflater, container, savedInstanceState);
-        ButterKnife.bind(this, view);
+        final FragmentEntitiesBinding binding = FragmentEntitiesBinding.bind(view);
+        recyclerView = binding.entitiesRecyclerview;
         final Context context = inflater.getContext();
         adapter = new EntitiesAdapter(context, TextUtils.isEmpty(category) ? getEntities() : getEntities(category));
         recyclerView.setLayoutManager(new LinearLayoutManager(context, LinearLayoutManager.VERTICAL, false));
@@ -204,19 +204,18 @@ public abstract class BaseEntitiesFragment<E extends MathEntity> extends BaseFra
     protected abstract boolean onMenuItemClicked(@Nonnull MenuItem item, @Nonnull E entity);
 
     public class EntityViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener, View.OnCreateContextMenuListener, MenuItem.OnMenuItemClickListener {
-        @BindView(R.id.entity_text)
         TextView textView;
-        @BindView(R.id.entity_description)
         TextView descriptionView;
         @Nullable
         private E entity;
 
-        public EntityViewHolder(@Nonnull View view) {
-            super(view);
+        public EntityViewHolder(@Nonnull FragmentEntitiesItemBinding binding) {
+            super(binding.getRoot());
             BaseActivity.fixFonts(itemView, typeface);
-            ButterKnife.bind(this, view);
-            view.setOnClickListener(this);
-            view.setOnCreateContextMenuListener(this);
+            textView = binding.entityText;
+            descriptionView = binding.entityDescription;
+            itemView.setOnClickListener(this);
+            itemView.setOnCreateContextMenuListener(this);
         }
 
         public void bind(@Nonnull E entity) {
@@ -266,7 +265,7 @@ public abstract class BaseEntitiesFragment<E extends MathEntity> extends BaseFra
 
         @Override
         public EntityViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
-            return new EntityViewHolder(inflater.inflate(R.layout.fragment_entities_item, parent, false));
+            return new EntityViewHolder(FragmentEntitiesItemBinding.inflate(inflater, parent, false));
         }
 
         @Override

app/src/main/java/org/solovyev/android/calculator/entities/BaseEntitiesRegistry.java

@@ -25,8 +25,8 @@ package org.solovyev.android.calculator.entities;
 import android.app.Application;
 import android.content.SharedPreferences;
 import android.os.Handler;
-import android.support.annotation.NonNull;
-import android.support.annotation.StringRes;
+import androidx.annotation.NonNull;
+import androidx.annotation.StringRes;
 
 import com.squareup.otto.Bus;
 

app/src/main/java/org/solovyev/android/calculator/entities/Category.java

@@ -1,6 +1,6 @@
 package org.solovyev.android.calculator.entities;
 
-import android.support.annotation.StringRes;
+import androidx.annotation.StringRes;
 
 import org.solovyev.common.math.MathEntity;
 

app/src/main/java/org/solovyev/android/calculator/entities/Entities.java

@@ -1,6 +1,6 @@
 package org.solovyev.android.calculator.entities;
 
-import android.support.annotation.NonNull;
+import androidx.annotation.NonNull;
 
 import org.solovyev.common.math.MathEntity;
 

app/src/main/java/org/solovyev/android/calculator/errors/FixableErrorFragment.java

@@ -3,10 +3,10 @@ package org.solovyev.android.calculator.errors;
 import android.app.Activity;
 import android.content.DialogInterface;
 import android.os.Bundle;
-import android.support.annotation.NonNull;
-import android.support.annotation.Nullable;
-import android.support.v4.app.FragmentManager;
-import android.support.v7.app.AlertDialog;
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import androidx.appcompat.app.AlertDialog;
+import androidx.fragment.app.FragmentManager;
 import org.solovyev.android.Check;
 import org.solovyev.android.calculator.*;
 

app/src/main/java/org/solovyev/android/calculator/errors/FixableErrorsActivity.java

@@ -26,8 +26,8 @@ import android.content.Context;
 import android.content.Intent;
 import android.content.SharedPreferences;
 import android.os.Bundle;
-import android.support.v4.app.Fragment;
-import android.support.v7.app.AppCompatActivity;
+import androidx.appcompat.app.AppCompatActivity;
+import androidx.fragment.app.Fragment;
 import org.solovyev.android.calculator.App;
 import org.solovyev.android.calculator.UiPreferences;
 import org.solovyev.common.msg.Message;

app/src/main/java/org/solovyev/android/calculator/floating/FloatingCalculatorActivity.java

@@ -27,11 +27,11 @@ import android.content.DialogInterface;
 import android.os.Build;
 import android.os.Bundle;
 import android.provider.Settings;
-import android.support.annotation.NonNull;
-import android.support.v4.app.FragmentActivity;
-import android.support.v7.app.AlertDialog;
-import android.support.v7.app.AppCompatActivity;
+import androidx.annotation.NonNull;
 
+import androidx.appcompat.app.AlertDialog;
+import androidx.appcompat.app.AppCompatActivity;
+import androidx.fragment.app.FragmentActivity;
 import org.solovyev.android.Check;
 import org.solovyev.android.calculator.App;
 import org.solovyev.android.calculator.BaseDialogFragment;

app/src/main/java/org/solovyev/android/calculator/floating/FloatingCalculatorService.java

@@ -29,7 +29,7 @@ import android.content.Context;
 import android.content.Intent;
 import android.content.SharedPreferences;
 import android.os.IBinder;
-import android.support.v4.app.NotificationCompat;
+import androidx.core.app.NotificationCompat;
 import android.util.DisplayMetrics;
 import android.view.WindowManager;
 import com.squareup.otto.Bus;
@@ -177,7 +177,7 @@ public class FloatingCalculatorService extends Service implements FloatingViewLi
         builder.setOngoing(true);
 
         final Intent intent = createShowWindowIntent(this);
-        builder.setContentIntent(PendingIntent.getBroadcast(this, 0, intent, PendingIntent.FLAG_UPDATE_CURRENT));
+        builder.setContentIntent(PendingIntent.getBroadcast(this, 0, intent, PendingIntent.FLAG_UPDATE_CURRENT | PendingIntent.FLAG_IMMUTABLE));
 
         final NotificationManager nm = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
         nm.notify(NOTIFICATION_ID, builder.build());

app/src/main/java/org/solovyev/android/calculator/floating/FloatingCalculatorView.java

@@ -32,7 +32,7 @@ import android.graphics.drawable.Drawable;
 import android.os.Build;
 import android.os.Parcel;
 import android.os.Parcelable;
-import android.support.annotation.NonNull;
+import androidx.annotation.NonNull;
 import android.util.DisplayMetrics;
 import android.view.ContextThemeWrapper;
 import android.view.Display;
@@ -209,7 +209,7 @@ public class FloatingCalculatorView {
             y = in.readInt();
         }
 
-        @android.support.annotation.Nullable
+        @androidx.annotation.Nullable
         public static State fromPrefs(@NonNull SharedPreferences prefs) {
             if(!prefs.contains("width")) {
                 return null;

app/src/main/java/org/solovyev/android/calculator/functions/BaseFunctionFragment.java

@@ -27,10 +27,8 @@ import android.content.Context;
 import android.content.DialogInterface;
 import android.graphics.Typeface;
 import android.os.Bundle;
-import android.support.annotation.LayoutRes;
-import android.support.annotation.NonNull;
-import android.support.design.widget.TextInputLayout;
-import android.support.v7.app.AlertDialog;
+import androidx.annotation.LayoutRes;
+import androidx.annotation.NonNull;
 import android.text.Editable;
 import android.text.TextUtils;
 import android.view.ContextMenu;
@@ -44,6 +42,8 @@ import android.view.ViewParent;
 import android.view.inputmethod.InputMethodManager;
 import android.widget.EditText;
 
+import androidx.appcompat.app.AlertDialog;
+import com.google.android.material.textfield.TextInputLayout;
 import org.solovyev.android.Check;
 import org.solovyev.android.calculator.AppComponent;
 import org.solovyev.android.calculator.BaseDialogFragment;
@@ -69,8 +69,6 @@ import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
 import javax.inject.Inject;
 
-import butterknife.BindView;
-import butterknife.ButterKnife;
 import jscl.math.function.IConstant;
 
 import static org.solovyev.android.calculator.functions.CppFunction.NO_ID;
@@ -86,20 +84,12 @@ public abstract class BaseFunctionFragment extends BaseDialogFragment implements
     private final FloatingKeyboardWindow keyboardWindow = new FloatingKeyboardWindow(null);
     @NonNull
     private final KeyboardUser keyboardUser = new KeyboardUser();
-    @BindView(R.id.function_params)
-    public
-    FunctionParamsView paramsView;
-    @BindView(R.id.function_name_label)
-    TextInputLayout nameLabel;
-    @BindView(R.id.function_name)
+    public FunctionParamsView paramsView;
+    public TextInputLayout nameLabel;
     public EditText nameView;
-    @BindView(R.id.function_body_label)
     public TextInputLayout bodyLabel;
-    @BindView(R.id.function_body)
     public EditTextCompat bodyView;
-    @BindView(R.id.function_description_label)
     public TextInputLayout descriptionLabel;
-    @BindView(R.id.function_description)
     public EditText descriptionView;
     @Inject
     Calculator calculator;
@@ -181,23 +171,20 @@ public abstract class BaseFunctionFragment extends BaseDialogFragment implements
         }
 
         final int id = v.getId();
-        switch (id) {
-            case R.id.function_name:
-                if (hasFocus) {
-                    clearError(nameLabel);
-                } else {
-                    validateName();
-                }
-                break;
-            case R.id.function_body:
-                if (hasFocus) {
-                    clearError(bodyLabel);
-                    showKeyboard();
-                } else {
-                    keyboardWindow.hide();
-                    validateBody();
-                }
-                break;
+        if (id == R.id.function_name) {
+            if (hasFocus) {
+                clearError(nameLabel);
+            } else {
+                validateName();
+            }
+        } else if (id == R.id.function_body) {
+            if (hasFocus) {
+                clearError(bodyLabel);
+                showKeyboard();
+            } else {
+                keyboardWindow.hide();
+                validateBody();
+            }
         }
     }
 
@@ -219,13 +206,10 @@ public abstract class BaseFunctionFragment extends BaseDialogFragment implements
 
     @Override
     public void onClick(View v) {
-        switch (v.getId()) {
-            case R.id.function_body:
-                showKeyboard();
-                break;
-            default:
-                super.onClick(v);
-                break;
+        if (v.getId() == R.id.function_body) {
+            showKeyboard();
+        } else {
+            super.onClick(v);
         }
     }
 
@@ -348,7 +332,13 @@ public abstract class BaseFunctionFragment extends BaseDialogFragment implements
     @Override
     protected View onCreateDialogView(@NonNull Context context, @NonNull LayoutInflater inflater, @Nullable Bundle savedInstanceState) {
         final View view = inflater.inflate(layout, null);
-        ButterKnife.bind(this, view);
+        paramsView = view.findViewById(R.id.function_params);
+        nameLabel = view.findViewById(R.id.function_name_label);
+        nameView = view.findViewById(R.id.function_name);
+        bodyLabel = view.findViewById(R.id.function_body_label);
+        bodyView = view.findViewById(R.id.function_body);
+        descriptionLabel = view.findViewById(R.id.function_description_label);
+        descriptionView = view.findViewById(R.id.function_description);
 
         if (savedInstanceState == null && function != null) {
             paramsView.addParams(function.getParameters());

app/src/main/java/org/solovyev/android/calculator/functions/CppFunction.java

@@ -2,7 +2,7 @@ package org.solovyev.android.calculator.functions;
 
 import android.os.Parcel;
 import android.os.Parcelable;
-import android.support.annotation.NonNull;
+import androidx.annotation.NonNull;
 import android.text.TextUtils;
 import jscl.math.function.CustomFunction;
 import jscl.math.function.IFunction;

app/src/main/java/org/solovyev/android/calculator/functions/EditFunctionFragment.java

@@ -4,10 +4,10 @@ import android.content.Context;
 import android.content.DialogInterface;
 import android.content.Intent;
 import android.os.Bundle;
-import android.support.annotation.NonNull;
-import android.support.v4.app.FragmentActivity;
-import android.support.v4.app.FragmentManager;
+import androidx.annotation.NonNull;
 import android.text.TextUtils;
+import androidx.fragment.app.FragmentActivity;
+import androidx.fragment.app.FragmentManager;
 import jscl.math.function.Function;
 import org.solovyev.android.Check;
 import org.solovyev.android.calculator.App;

app/src/main/java/org/solovyev/android/calculator/functions/FunctionCategory.java

@@ -22,7 +22,7 @@
 
 package org.solovyev.android.calculator.functions;
 
-import android.support.annotation.StringRes;
+import androidx.annotation.StringRes;
 
 import org.solovyev.android.calculator.R;
 import org.solovyev.android.calculator.entities.Category;

app/src/main/java/org/solovyev/android/calculator/functions/FunctionParamsView.java

@@ -22,6 +22,7 @@
 
 package org.solovyev.android.calculator.functions;
 
+import com.google.android.material.textfield.TextInputLayout;
 import org.solovyev.android.Check;
 import org.solovyev.android.calculator.App;
 import org.solovyev.android.calculator.Preferences;
@@ -33,8 +34,7 @@ import android.content.res.Resources;
 import android.os.Build;
 import android.os.Parcel;
 import android.os.Parcelable;
-import android.support.annotation.NonNull;
-import android.support.design.widget.TextInputLayout;
+import androidx.annotation.NonNull;
 import android.util.AttributeSet;
 import android.util.TypedValue;
 import android.view.Gravity;
@@ -132,7 +132,7 @@ public class FunctionParamsView extends LinearLayout {
         addButton.setScaleType(ImageView.ScaleType.CENTER_INSIDE);
         addButton.setPadding(imageButtonPadding, imageButtonPadding, imageButtonPadding, imageButtonPadding);
         final TypedValue value = new TypedValue();
-        if (getContext().getTheme().resolveAttribute(R.attr.selectableItemBackgroundBorderless, value, true)) {
+        if (getContext().getTheme().resolveAttribute(androidx.appcompat.R.attr.selectableItemBackgroundBorderless, value, true)) {
             addButton.setBackgroundResource(value.resourceId);
         }
         return addButton;

app/src/main/java/org/solovyev/android/calculator/functions/FunctionsActivity.java

@@ -24,7 +24,7 @@ package org.solovyev.android.calculator.functions;
 
 import android.content.Context;
 import android.os.Bundle;
-import android.support.annotation.NonNull;
+import androidx.annotation.NonNull;
 import android.view.View;
 import org.solovyev.android.calculator.App;
 import org.solovyev.android.calculator.BaseActivity;
@@ -91,4 +91,4 @@ public class FunctionsActivity extends BaseActivity {
 
     public static final class Dialog extends FunctionsActivity {
     }
-}
+}

app/src/main/java/org/solovyev/android/calculator/functions/FunctionsFragment.java

@@ -24,9 +24,9 @@ package org.solovyev.android.calculator.functions;
 
 import android.content.DialogInterface;
 import android.os.Bundle;
-import android.support.annotation.NonNull;
-import android.support.v4.app.FragmentActivity;
+import androidx.annotation.NonNull;
 import android.view.*;
+import androidx.fragment.app.FragmentActivity;
 import com.squareup.otto.Bus;
 import com.squareup.otto.Subscribe;
 import jscl.math.function.Function;
@@ -79,25 +79,25 @@ public class FunctionsFragment extends BaseEntitiesFragment<Function> {
     @Override
     protected boolean onMenuItemClicked(@Nonnull MenuItem item, @Nonnull final Function function) {
         final FragmentActivity activity = getActivity();
-        switch (item.getItemId()) {
-            case R.string.c_use:
-                onClick(function);
-                return true;
-            case R.string.cpp_edit:
-                if (function instanceof IFunction) {
-                    EditFunctionFragment.show(CppFunction.builder((IFunction) function).build(),
+        int itemId = item.getItemId();
+        if (itemId == R.string.c_use) {
+            onClick(function);
+            return true;
+        } else if (itemId == R.string.cpp_edit) {
+            if (function instanceof IFunction) {
+                EditFunctionFragment.show(CppFunction.builder((IFunction) function).build(),
                         activity.getSupportFragmentManager());
+            }
+            return true;
+        } else if (itemId == R.string.cpp_delete) {
+            RemovalConfirmationDialog.showForFunction(getActivity(), function.getName(), new DialogInterface.OnClickListener() {
+                @Override
+                public void onClick(DialogInterface dialog, int which) {
+                    Check.isTrue(which == DialogInterface.BUTTON_POSITIVE);
+                    registry.remove(function);
                 }
-                return true;
-            case R.string.cpp_delete:
-                RemovalConfirmationDialog.showForFunction(getActivity(), function.getName(), new DialogInterface.OnClickListener() {
-                    @Override
-                    public void onClick(DialogInterface dialog, int which) {
-                        Check.isTrue(which == DialogInterface.BUTTON_POSITIVE);
-                        registry.remove(function);
-                    }
-                });
-                return true;
+            });
+            return true;
         }
         return false;
     }

app/src/main/java/org/solovyev/android/calculator/functions/FunctionsRegistry.java

@@ -24,7 +24,7 @@ package org.solovyev.android.calculator.functions;
 
 import static android.text.TextUtils.isEmpty;
 
-import android.support.annotation.NonNull;
+import androidx.annotation.NonNull;
 
 import org.simpleframework.xml.Serializer;
 import org.simpleframework.xml.core.Persister;

app/src/main/java/org/solovyev/android/calculator/history/BaseHistoryFragment.java

@@ -29,11 +29,7 @@ import android.app.Activity;
 import android.content.Context;
 import android.graphics.Typeface;
 import android.os.Bundle;
-import android.support.annotation.NonNull;
-import android.support.v4.app.FragmentActivity;
-import android.support.v7.widget.DividerItemDecoration;
-import android.support.v7.widget.LinearLayoutManager;
-import android.support.v7.widget.RecyclerView;
+import androidx.annotation.NonNull;
 import android.text.ClipboardManager;
 import android.text.format.DateUtils;
 import android.view.ContextMenu;
@@ -43,6 +39,10 @@ import android.view.View;
 import android.view.ViewGroup;
 import android.widget.TextView;
 
+import androidx.fragment.app.FragmentActivity;
+import androidx.recyclerview.widget.DividerItemDecoration;
+import androidx.recyclerview.widget.LinearLayoutManager;
+import androidx.recyclerview.widget.RecyclerView;
 import com.squareup.otto.Bus;
 import com.squareup.otto.Subscribe;
 
@@ -53,6 +53,8 @@ import org.solovyev.android.calculator.BaseFragment;
 import org.solovyev.android.calculator.CalculatorActivity;
 import org.solovyev.android.calculator.Editor;
 import org.solovyev.android.calculator.R;
+import org.solovyev.android.calculator.databinding.FragmentHistoryBinding;
+import org.solovyev.android.calculator.databinding.FragmentHistoryItemBinding;
 import org.solovyev.android.calculator.jscl.JsclOperation;
 import org.solovyev.common.text.Strings;
 
@@ -62,8 +64,6 @@ import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
 import javax.inject.Inject;
 
-import butterknife.BindView;
-import butterknife.ButterKnife;
 
 public abstract class BaseHistoryFragment extends BaseFragment {
     private final boolean recentHistory;
@@ -75,7 +75,6 @@ public abstract class BaseHistoryFragment extends BaseFragment {
     Bus bus;
     @Inject
     Typeface typeface;
-    @BindView(R.id.history_recyclerview)
     RecyclerView recyclerView;
     private HistoryAdapter adapter;
 
@@ -111,7 +110,8 @@ public abstract class BaseHistoryFragment extends BaseFragment {
     @Override
     public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
         final View view = super.onCreateView(inflater, container, savedInstanceState);
-        ButterKnife.bind(this, view);
+        FragmentHistoryBinding binding = FragmentHistoryBinding.bind(view);
+        recyclerView = binding.historyRecyclerview;
         final Context context = inflater.getContext();
         adapter = new HistoryAdapter(context);
         bus.register(adapter);
@@ -156,21 +156,20 @@ public abstract class BaseHistoryFragment extends BaseFragment {
     public class HistoryViewHolder extends RecyclerView.ViewHolder implements View.OnCreateContextMenuListener, View.OnClickListener, MenuItem.OnMenuItemClickListener {
 
         private static final int DATETIME_FORMAT = DateUtils.FORMAT_SHOW_TIME | DateUtils.FORMAT_SHOW_DATE | DateUtils.FORMAT_ABBREV_MONTH | DateUtils.FORMAT_ABBREV_TIME;
-        @BindView(R.id.history_item_value)
         TextView valueView;
-        @BindView(R.id.history_item_comment)
         TextView commentView;
-        @BindView(R.id.history_item_time)
         TextView timeView;
         @Nullable
         private HistoryState state;
 
-        public HistoryViewHolder(View view) {
-            super(view);
-            BaseActivity.fixFonts(view, typeface);
-            ButterKnife.bind(this, view);
-            view.setOnCreateContextMenuListener(this);
-            view.setOnClickListener(this);
+        public HistoryViewHolder(@NonNull FragmentHistoryItemBinding binding) {
+            super(binding.getRoot());
+            BaseActivity.fixFonts(binding.getRoot(), typeface);
+            valueView = binding.historyItemValue;
+            commentView = binding.historyItemComment;
+            timeView = binding.historyItemTime;
+            itemView.setOnCreateContextMenuListener(this);
+            itemView.setOnClickListener(this);
         }
 
         void bind(@Nonnull HistoryState state) {
@@ -217,25 +216,25 @@ public abstract class BaseHistoryFragment extends BaseFragment {
         @Override
         public boolean onMenuItemClick(MenuItem item) {
             Check.isNotNull(state);
-            switch (item.getItemId()) {
-                case R.string.c_use:
-                    useState(state);
-                    return true;
-                case R.string.c_copy_expression:
-                    copyExpression(state);
-                    return true;
-                case R.string.c_copy_result:
-                    copyResult(state);
-                    return true;
-                case R.string.cpp_edit:
-                    EditHistoryFragment.show(state, false, getFragmentManager());
-                    return true;
-                case R.string.c_save:
-                    EditHistoryFragment.show(state, true, getFragmentManager());
-                    return true;
-                case R.string.cpp_delete:
-                    history.removeSaved(state);
-                    return true;
+            int itemId = item.getItemId();
+            if (itemId == R.string.c_use) {
+                useState(state);
+                return true;
+            } else if (itemId == R.string.c_copy_expression) {
+                copyExpression(state);
+                return true;
+            } else if (itemId == R.string.c_copy_result) {
+                copyResult(state);
+                return true;
+            } else if (itemId == R.string.cpp_edit) {
+                EditHistoryFragment.show(state, false, getParentFragmentManager());
+                return true;
+            } else if (itemId == R.string.c_save) {
+                EditHistoryFragment.show(state, true, getParentFragmentManager());
+                return true;
+            } else if (itemId == R.string.cpp_delete) {
+                history.removeSaved(state);
+                return true;
             }
             return false;
         }
@@ -262,7 +261,7 @@ public abstract class BaseHistoryFragment extends BaseFragment {
 
         @Override
         public HistoryViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
-            return new HistoryViewHolder(inflater.inflate(R.layout.fragment_history_item, parent, false));
+            return new HistoryViewHolder(FragmentHistoryItemBinding.inflate(inflater, parent, false));
         }
 
         @Override

app/src/main/java/org/solovyev/android/calculator/history/EditHistoryFragment.java

@@ -4,22 +4,21 @@ import android.annotation.SuppressLint;
 import android.content.Context;
 import android.content.DialogInterface;
 import android.os.Bundle;
-import android.support.annotation.NonNull;
-import android.support.annotation.Nullable;
-import android.support.v4.app.FragmentManager;
-import android.support.v7.app.AlertDialog;
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
 import android.view.LayoutInflater;
 import android.view.View;
 import android.widget.EditText;
 import android.widget.TextView;
 
-import butterknife.BindView;
-import butterknife.ButterKnife;
+import androidx.appcompat.app.AlertDialog;
+import androidx.fragment.app.FragmentManager;
 import org.solovyev.android.calculator.AppComponent;
 import org.solovyev.android.calculator.BaseDialogFragment;
 import org.solovyev.android.calculator.R;
 
 import javax.inject.Inject;
+import org.solovyev.android.calculator.databinding.FragmentHistoryEditBinding;
 
 public class EditHistoryFragment extends BaseDialogFragment {
 
@@ -33,10 +32,7 @@ public class EditHistoryFragment extends BaseDialogFragment {
 
     boolean newState;
 
-    @BindView(R.id.history_expression)
     TextView expressionView;
-
-    @BindView(R.id.history_comment)
     EditText commentView;
 
     public static void show(@NonNull HistoryState state, boolean newState, @NonNull FragmentManager fm) {
@@ -95,12 +91,13 @@ public class EditHistoryFragment extends BaseDialogFragment {
     @NonNull
     @Override
     protected View onCreateDialogView(@NonNull Context context, @NonNull LayoutInflater inflater, @Nullable Bundle savedInstanceState) {
-        final View view = inflater.inflate(R.layout.fragment_history_edit, null);
-        ButterKnife.bind(this, view);
+        final FragmentHistoryEditBinding binding = FragmentHistoryEditBinding.inflate(inflater, null, false);
+        expressionView = binding.historyExpression;
+        commentView = binding.historyComment;
         if (savedInstanceState == null) {
             expressionView.setText(BaseHistoryFragment.getHistoryText(state));
             commentView.setText(state.getComment());
         }
-        return view;
+        return binding.getRoot();
     }
 }

app/src/main/java/org/solovyev/android/calculator/history/History.java

@@ -27,7 +27,7 @@ import static android.text.TextUtils.isEmpty;
 import android.app.Application;
 import android.content.SharedPreferences;
 import android.os.Handler;
-import android.support.annotation.NonNull;
+import androidx.annotation.NonNull;
 import android.text.TextUtils;
 
 import com.google.common.base.Strings;
@@ -466,4 +466,4 @@ public class History {
             });
         }
     }
-}
+}

app/src/main/java/org/solovyev/android/calculator/history/HistoryActivity.java

@@ -25,11 +25,11 @@ package org.solovyev.android.calculator.history;
 import android.content.Context;
 import android.content.DialogInterface;
 import android.os.Bundle;
-import android.support.annotation.NonNull;
-import android.support.v4.app.Fragment;
-import android.support.v7.app.AlertDialog;
+import androidx.annotation.NonNull;
 import android.view.View;
 
+import androidx.appcompat.app.AlertDialog;
+import androidx.fragment.app.Fragment;
 import org.solovyev.android.calculator.App;
 import org.solovyev.android.calculator.AppComponent;
 import org.solovyev.android.calculator.BaseActivity;

app/src/main/java/org/solovyev/android/calculator/history/HistoryState.java

@@ -2,7 +2,7 @@ package org.solovyev.android.calculator.history;
 
 import android.os.Parcel;
 import android.os.Parcelable;
-import android.support.annotation.NonNull;
+import androidx.annotation.NonNull;
 import android.text.TextUtils;
 
 import org.json.JSONException;

app/src/main/java/org/solovyev/android/calculator/history/RecentHistory.java

@@ -1,7 +1,7 @@
 package org.solovyev.android.calculator.history;
 
-import android.support.annotation.NonNull;
-import android.support.annotation.Nullable;
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
 import org.solovyev.android.Check;
 
 import java.util.Collections;

app/src/main/java/org/solovyev/android/calculator/jscl/JsclOperation.java

@@ -23,7 +23,7 @@
 package org.solovyev.android.calculator.jscl;
 
 
-import android.support.annotation.Nullable;
+import androidx.annotation.Nullable;
 import jscl.MathEngine;
 import jscl.math.Generic;
 import jscl.text.ParseException;

app/src/main/java/org/solovyev/android/calculator/json/Json.java

@@ -2,7 +2,7 @@ package org.solovyev.android.calculator.json;
 
 import static android.text.TextUtils.isEmpty;
 
-import android.support.annotation.NonNull;
+import androidx.annotation.NonNull;
 import android.util.Log;
 
 import org.json.JSONArray;

app/src/main/java/org/solovyev/android/calculator/keyboard/BaseFloatingKeyboard.java

@@ -3,10 +3,10 @@ package org.solovyev.android.calculator.keyboard;
 import android.content.res.Resources;
 import android.graphics.Color;
 import android.os.Build;
-import android.support.annotation.ColorInt;
-import android.support.annotation.DrawableRes;
-import android.support.annotation.IdRes;
-import android.support.annotation.NonNull;
+import androidx.annotation.ColorInt;
+import androidx.annotation.DrawableRes;
+import androidx.annotation.IdRes;
+import androidx.annotation.NonNull;
 import android.text.TextUtils;
 import android.util.TypedValue;
 import android.view.View;

app/src/main/java/org/solovyev/android/calculator/keyboard/BaseKeyboardUi.java

@@ -11,8 +11,8 @@ import android.app.Activity;
 import android.app.Application;
 import android.content.Context;
 import android.content.SharedPreferences;
-import android.support.annotation.NonNull;
-import android.support.annotation.Nullable;
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
 import android.text.TextUtils;
 import android.util.DisplayMetrics;
 import android.util.TypedValue;

app/src/main/java/org/solovyev/android/calculator/keyboard/FloatingKeyboard.java

@@ -2,7 +2,7 @@ package org.solovyev.android.calculator.keyboard;
 
 import android.content.Context;
 import android.graphics.Typeface;
-import android.support.annotation.NonNull;
+import androidx.annotation.NonNull;
 import android.view.ViewGroup;
 import android.widget.EditText;
 

app/src/main/java/org/solovyev/android/calculator/keyboard/FloatingKeyboardWindow.java

@@ -4,8 +4,8 @@ import android.app.Dialog;
 import android.content.Context;
 import android.content.res.Configuration;
 import android.content.res.Resources;
-import android.support.annotation.NonNull;
-import android.support.annotation.Nullable;
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
 import android.view.Gravity;
 import android.view.View;
 import android.view.Window;

app/src/main/java/org/solovyev/android/calculator/keyboard/FloatingNumberKeyboard.java

@@ -1,7 +1,7 @@
 package org.solovyev.android.calculator.keyboard;
 
-import android.support.annotation.IdRes;
-import android.support.annotation.NonNull;
+import androidx.annotation.IdRes;
+import androidx.annotation.NonNull;
 import android.view.View;
 import android.widget.EditText;
 import android.widget.LinearLayout;
@@ -93,13 +93,13 @@ public class FloatingNumberKeyboard extends BaseFloatingKeyboard {
         @Override
         public void onClick(View v) {
             final EditText editor = getUser().getEditor();
-            switch (v.getId()) {
-                case R.id.cpp_kb_button_clear:
-                    editor.setText("");
-                    return;
-                case R.id.cpp_kb_button_close:
-                    getUser().done();
-                    return;
+            int id = v.getId();
+            if (id == R.id.cpp_kb_button_clear) {
+                editor.setText("");
+                return;
+            } else if (id == R.id.cpp_kb_button_close) {
+                getUser().done();
+                return;
             }
             if (v instanceof TextView) {
                 insertText(((TextView) v).getText());

app/src/main/java/org/solovyev/android/calculator/keyboard/KeyboardUi.java

@@ -3,10 +3,8 @@ package org.solovyev.android.calculator.keyboard;
 import android.app.Activity;
 import android.app.Application;
 import android.content.SharedPreferences;
-import android.support.annotation.Nullable;
+import androidx.annotation.Nullable;
 import android.view.View;
-import butterknife.BindView;
-import butterknife.ButterKnife;
 import com.squareup.otto.Bus;
 import com.squareup.otto.Subscribe;
 import jscl.NumeralBase;
@@ -24,25 +22,15 @@ import static org.solovyev.android.views.dragbutton.DragDirection.*;
 
 public class KeyboardUi extends BaseKeyboardUi {
 
-    @BindView(R.id.cpp_button_0)
     public DirectionDragButton button0;
-    @BindView(R.id.cpp_button_1)
     public DirectionDragButton button1;
-    @BindView(R.id.cpp_button_2)
     public DirectionDragButton button2;
-    @BindView(R.id.cpp_button_3)
     public DirectionDragButton button3;
-    @BindView(R.id.cpp_button_4)
     public DirectionDragButton button4;
-    @BindView(R.id.cpp_button_5)
     public DirectionDragButton button5;
-    @BindView(R.id.cpp_button_6)
     public DirectionDragButton button6;
-    @BindView(R.id.cpp_button_7)
     public DirectionDragButton button7;
-    @BindView(R.id.cpp_button_8)
     public DirectionDragButton button8;
-    @BindView(R.id.cpp_button_9)
     public DirectionDragButton button9;
     @Inject
     Engine engine;
@@ -52,35 +40,22 @@ public class KeyboardUi extends BaseKeyboardUi {
     Bus bus;
     @Inject
     PartialKeyboardUi partialUi;
-    @BindView(R.id.cpp_button_vars)
     DirectionDragButton variablesButton;
     @Nullable
-    @BindView(R.id.cpp_button_operators)
     DirectionDragButton operatorsButton;
-    @BindView(R.id.cpp_button_functions)
     DirectionDragButton functionsButton;
-    @BindView(R.id.cpp_button_history)
     DirectionDragButton historyButton;
-    @BindView(R.id.cpp_button_multiplication)
     DirectionDragButton multiplicationButton;
-    @BindView(R.id.cpp_button_plus)
     DirectionDragButton plusButton;
-    @BindView(R.id.cpp_button_subtraction)
     DirectionDragButton subtractionButton;
-    @BindView(R.id.cpp_button_division)
     DirectionDragButton divisionButton;
-    @BindView(R.id.cpp_button_period)
     DirectionDragButton periodButton;
-    @BindView(R.id.cpp_button_round_brackets)
     DirectionDragButton bracketsButton;
     @Nullable
-    @BindView(R.id.cpp_button_like)
     DirectionDragButton likeButton;
     @Nullable
-    @BindView(R.id.cpp_button_percent)
     DirectionDragButton percentButton;
     @Nullable
-    @BindView(R.id.cpp_button_memory)
     DirectionDragButton memoryButton;
 
     @Inject
@@ -101,7 +76,30 @@ public class KeyboardUi extends BaseKeyboardUi {
     public void onCreateView(@Nonnull Activity activity, @Nonnull View view) {
         super.onCreateView(activity, view);
         partialUi.onCreateView(activity, view);
-        ButterKnife.bind(this, view);
+        button0 = view.findViewById(R.id.cpp_button_0);
+        button1 = view.findViewById(R.id.cpp_button_1);
+        button2 = view.findViewById(R.id.cpp_button_2);
+        button3 = view.findViewById(R.id.cpp_button_3);
+        button4 = view.findViewById(R.id.cpp_button_4);
+        button5 = view.findViewById(R.id.cpp_button_5);
+        button6 = view.findViewById(R.id.cpp_button_6);
+        button7 = view.findViewById(R.id.cpp_button_7);
+        button8 = view.findViewById(R.id.cpp_button_8);
+        button9 = view.findViewById(R.id.cpp_button_9);
+
+        variablesButton = view.findViewById(R.id.cpp_button_vars);
+        operatorsButton = view.findViewById(R.id.cpp_button_operators);
+        functionsButton = view.findViewById(R.id.cpp_button_functions);
+        historyButton = view.findViewById(R.id.cpp_button_history);
+        multiplicationButton = view.findViewById(R.id.cpp_button_multiplication);
+        plusButton = view.findViewById(R.id.cpp_button_plus);
+        subtractionButton = view.findViewById(R.id.cpp_button_subtraction);
+        divisionButton = view.findViewById(R.id.cpp_button_division);
+        periodButton = view.findViewById(R.id.cpp_button_period);
+        bracketsButton = view.findViewById(R.id.cpp_button_round_brackets);
+        likeButton = view.findViewById(R.id.cpp_button_like);
+        percentButton = view.findViewById(R.id.cpp_button_percent);
+        memoryButton = view.findViewById(R.id.cpp_button_memory);
 
         prepareButton(variablesButton);
         prepareButton(operatorsButton);
@@ -169,4 +167,4 @@ public class KeyboardUi extends BaseKeyboardUi {
     public void onNumberModeChanged(@Nonnull Keyboard.NumberModeChangedEvent e) {
         updateNumberMode(e.mode);
     }
-}
+}

app/src/main/java/org/solovyev/android/calculator/keyboard/PartialKeyboardUi.java

@@ -3,8 +3,8 @@ package org.solovyev.android.calculator.keyboard;
 import android.app.Activity;
 import android.app.Application;
 import android.content.SharedPreferences;
-import android.support.annotation.NonNull;
-import android.support.annotation.Nullable;
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
 import android.view.View;
 
 import org.solovyev.android.calculator.R;
@@ -14,28 +14,20 @@ import org.solovyev.android.views.dragbutton.DirectionDragButton;
 import javax.annotation.Nonnull;
 import javax.inject.Inject;
 
-import butterknife.BindView;
-import butterknife.ButterKnife;
-
 import static org.solovyev.android.calculator.Preferences.Gui.vibrateOnKeypress;
 import static org.solovyev.android.views.dragbutton.DragDirection.down;
 
 public class PartialKeyboardUi extends BaseKeyboardUi {
 
     @Nullable
-    @BindView(R.id.cpp_button_right)
     DirectionDragButton rightButton;
     @Nullable
-    @BindView(R.id.cpp_button_left)
     DirectionDragButton leftButton;
     @Nullable
-    @BindView(R.id.cpp_button_clear)
     DirectionDragButton clearButton;
     @Nullable
-    @BindView(R.id.cpp_button_erase)
     DirectionDragButton eraseButton;
     @Nullable
-    @BindView(R.id.cpp_button_equals)
     DirectionDragButton equalsButton;
     @Nullable
     EditorLongClickEraser longClickEraser;
@@ -48,7 +40,11 @@ public class PartialKeyboardUi extends BaseKeyboardUi {
     @Override
     public void onCreateView(@Nonnull Activity activity, @Nonnull View view) {
         super.onCreateView(activity, view);
-        ButterKnife.bind(this, view);
+        rightButton = view.findViewById(R.id.cpp_button_right);
+        leftButton = view.findViewById(R.id.cpp_button_left);
+        clearButton = view.findViewById(R.id.cpp_button_clear);
+        eraseButton = view.findViewById(R.id.cpp_button_erase);
+        equalsButton = view.findViewById(R.id.cpp_button_equals);
         prepareButton(rightButton);
         prepareButton(leftButton);
         prepareButton(equalsButton);

app/src/main/java/org/solovyev/android/calculator/language/Language.java

@@ -1,7 +1,7 @@
 package org.solovyev.android.calculator.language;
 
 import android.content.Context;
-import android.support.annotation.NonNull;
+import androidx.annotation.NonNull;
 import android.text.TextUtils;
 import org.solovyev.android.calculator.R;
 import org.solovyev.android.calculator.preferences.PreferenceEntry;

app/src/main/java/org/solovyev/android/calculator/math/MathType.java

@@ -22,7 +22,7 @@
 
 package org.solovyev.android.calculator.math;
 
-import android.support.annotation.NonNull;
+import androidx.annotation.NonNull;
 import jscl.JsclMathEngine;
 import jscl.NumeralBase;
 import jscl.math.function.Constants;

app/src/main/java/org/solovyev/android/calculator/memory/Memory.java

@@ -1,7 +1,7 @@
 package org.solovyev.android.calculator.memory;
 
 import android.os.Handler;
-import android.support.annotation.NonNull;
+import androidx.annotation.NonNull;
 import android.text.TextUtils;
 import android.util.Log;
 

app/src/main/java/org/solovyev/android/calculator/operators/OperatorCategory.java

@@ -22,7 +22,7 @@
 
 package org.solovyev.android.calculator.operators;
 
-import android.support.annotation.StringRes;
+import androidx.annotation.StringRes;
 import jscl.math.operator.*;
 import org.solovyev.android.calculator.R;
 import org.solovyev.android.calculator.entities.Category;

app/src/main/java/org/solovyev/android/calculator/operators/OperatorsActivity.java

@@ -23,7 +23,7 @@
 package org.solovyev.android.calculator.operators;
 
 import android.content.Context;
-import android.support.annotation.NonNull;
+import androidx.annotation.NonNull;
 
 import org.solovyev.android.calculator.App;
 import org.solovyev.android.calculator.BaseActivity;

app/src/main/java/org/solovyev/android/calculator/operators/OperatorsFragment.java

@@ -22,7 +22,7 @@
 
 package org.solovyev.android.calculator.operators;
 
-import android.support.annotation.NonNull;
+import androidx.annotation.NonNull;
 import android.view.ContextMenu;
 import android.view.MenuItem;
 import jscl.math.operator.Operator;
@@ -78,10 +78,9 @@ public class OperatorsFragment extends BaseEntitiesFragment<Operator> {
 
     @Override
     protected boolean onMenuItemClicked(@Nonnull MenuItem item, @Nonnull Operator operator) {
-        switch (item.getItemId()) {
-            case R.string.c_use:
-                onClick(operator);
-                return true;
+        if (item.getItemId() == R.string.c_use) {
+            onClick(operator);
+            return true;
         }
 
         return false;

app/src/main/java/org/solovyev/android/calculator/operators/OperatorsRegistry.java

@@ -22,7 +22,7 @@
 
 package org.solovyev.android.calculator.operators;
 
-import android.support.annotation.NonNull;
+import androidx.annotation.NonNull;
 import jscl.JsclMathEngine;
 import jscl.math.operator.Operator;
 import org.solovyev.android.calculator.R;

app/src/main/java/org/solovyev/android/calculator/operators/PostfixFunctionsRegistry.java

@@ -22,7 +22,7 @@
 
 package org.solovyev.android.calculator.operators;
 
-import android.support.annotation.NonNull;
+import androidx.annotation.NonNull;
 import jscl.JsclMathEngine;
 import jscl.math.operator.Operator;
 import org.solovyev.android.calculator.R;

app/src/main/java/org/solovyev/android/calculator/plot/PlotActivity.java

@@ -1,18 +1,19 @@
 package org.solovyev.android.calculator.plot;
 
 import android.os.Bundle;
-import android.support.v4.app.FragmentManager;
-import android.support.v4.app.FragmentTransaction;
-import android.support.v4.content.ContextCompat;
+import androidx.core.content.ContextCompat;
 import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
 import android.widget.Toast;
 
+import androidx.fragment.app.FragmentManager;
+import androidx.fragment.app.FragmentTransaction;
 import org.solovyev.android.calculator.AppComponent;
 import org.solovyev.android.calculator.BaseActivity;
 import org.solovyev.android.calculator.BaseFragment;
 import org.solovyev.android.calculator.R;
+import org.solovyev.android.calculator.databinding.FragmentPlotBinding;
 import org.solovyev.android.plotter.Dimensions;
 import org.solovyev.android.plotter.PlotData;
 import org.solovyev.android.plotter.PlotViewFrame;
@@ -21,8 +22,6 @@ import org.solovyev.android.plotter.Plotter;
 import javax.annotation.Nonnull;
 import javax.inject.Inject;
 
-import butterknife.BindView;
-import butterknife.ButterKnife;
 
 public class PlotActivity extends BaseActivity {
 
@@ -32,7 +31,6 @@ public class PlotActivity extends BaseActivity {
 
         @Inject
         Plotter plotter;
-        @BindView(R.id.plot_view_frame)
         PlotViewFrame plotView;
 
         public MyFragment() {
@@ -49,7 +47,8 @@ public class PlotActivity extends BaseActivity {
         public View onCreateView(LayoutInflater inflater, ViewGroup container,
             Bundle savedInstanceState) {
             final View view = super.onCreateView(inflater, container, savedInstanceState);
-            ButterKnife.bind(this, view);
+            final FragmentPlotBinding binding = FragmentPlotBinding.bind(view);
+            plotView = binding.plotViewFrame;
 
             final PlotData pd = plotter.getPlotData();
             pd.axisStyle.backgroundColor = ContextCompat.getColor(getActivity(), R.color.cpp_bg);

app/src/main/java/org/solovyev/android/calculator/plot/PlotDimensionsFragment.java

@@ -1,14 +1,10 @@
 package org.solovyev.android.calculator.plot;
 
-import android.annotation.SuppressLint;
 import android.content.Context;
 import android.content.DialogInterface;
 import android.graphics.RectF;
 import android.os.Bundle;
-import android.support.annotation.NonNull;
-import android.support.design.widget.TextInputLayout;
-import android.support.v4.app.FragmentManager;
-import android.support.v7.app.AlertDialog;
+import androidx.annotation.NonNull;
 import android.text.Editable;
 import android.text.TextUtils;
 import android.text.TextWatcher;
@@ -19,24 +15,22 @@ import android.view.inputmethod.EditorInfo;
 import android.view.inputmethod.InputMethodManager;
 import android.widget.EditText;
 import android.widget.TextView;
-
+import androidx.appcompat.app.AlertDialog;
+import androidx.fragment.app.FragmentManager;
+import com.google.android.material.textfield.TextInputLayout;
+import java.util.Locale;
+import javax.annotation.Nonnull;
+import javax.inject.Inject;
 import org.solovyev.android.calculator.App;
 import org.solovyev.android.calculator.AppComponent;
 import org.solovyev.android.calculator.BaseDialogFragment;
 import org.solovyev.android.calculator.BaseFragment;
 import org.solovyev.android.calculator.R;
+import org.solovyev.android.calculator.databinding.FragmentPlotDimensionsBinding;
 import org.solovyev.android.plotter.Check;
 import org.solovyev.android.plotter.Plot;
 import org.solovyev.android.plotter.Plotter;
 
-import java.util.Locale;
-
-import javax.annotation.Nonnull;
-import javax.inject.Inject;
-
-import butterknife.BindView;
-import butterknife.ButterKnife;
-
 public class PlotDimensionsFragment extends BaseDialogFragment
     implements TextView.OnEditorActionListener {
     private static final String ARG_BOUNDS = "arg-bounds";
@@ -77,23 +71,14 @@ public class PlotDimensionsFragment extends BaseDialogFragment
 
     @Inject
     Plotter plotter;
-    @BindView(R.id.plot_x_min)
     EditText xMin;
-    @BindView(R.id.plot_x_min_label)
     TextInputLayout xMinLabel;
-    @BindView(R.id.plot_x_max)
     EditText xMax;
-    @BindView(R.id.plot_x_max_label)
     TextInputLayout xMaxLabel;
-    @BindView(R.id.plot_y_min)
     EditText yMin;
-    @BindView(R.id.plot_y_min_label)
     TextInputLayout yMinLabel;
-    @BindView(R.id.plot_y_max)
     EditText yMax;
-    @BindView(R.id.plot_y_max_label)
     TextInputLayout yMaxLabel;
-    @BindView(R.id.y_bounds)
     View yBounds;
     @NonNull
     private RectF bounds = new RectF();
@@ -160,9 +145,17 @@ public class PlotDimensionsFragment extends BaseDialogFragment
     @Override
     protected View onCreateDialogView(@NonNull Context context, @NonNull LayoutInflater inflater,
         Bundle savedInstanceState) {
-        @SuppressLint("InflateParams") final View view =
-            LayoutInflater.from(context).inflate(R.layout.fragment_plot_dimensions, null);
-        ButterKnife.bind(this, view);
+        final FragmentPlotDimensionsBinding binding = FragmentPlotDimensionsBinding.inflate(inflater, null, false);
+
+        xMin = binding.plotXMin;
+        xMinLabel = binding.plotXMinLabel;
+        xMax = binding.plotXMax;
+        xMaxLabel = binding.plotXMaxLabel;
+        yMin = binding.plotYMin;
+        yMinLabel = binding.plotYMinLabel;
+        yMax = binding.plotYMax;
+        yMaxLabel = binding.plotYMaxLabel;
+        yBounds = binding.yBounds;
 
         setDimension(xMin, bounds.left);
         setDimension(xMax, bounds.right);
@@ -175,7 +168,7 @@ public class PlotDimensionsFragment extends BaseDialogFragment
         if (d3) {
             yBounds.setVisibility(View.GONE);
         }
-        return view;
+        return binding.getRoot();
     }
 
     @Override
@@ -284,4 +277,4 @@ public class PlotDimensionsFragment extends BaseDialogFragment
         }
         return false;
     }
-}
+}

app/src/main/java/org/solovyev/android/calculator/plot/PlotEditFunctionFragment.java

@@ -3,19 +3,20 @@ package org.solovyev.android.calculator.plot;
 import android.content.Context;
 import android.content.DialogInterface;
 import android.os.Bundle;
-import android.support.annotation.NonNull;
-import android.support.annotation.Nullable;
-import android.support.v4.app.FragmentManager;
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
 import android.view.LayoutInflater;
 import android.view.View;
 import android.widget.SeekBar;
 import android.widget.TextView;
 
+import androidx.fragment.app.FragmentManager;
 import org.solovyev.android.Check;
 import org.solovyev.android.calculator.App;
 import org.solovyev.android.calculator.AppComponent;
 import org.solovyev.android.calculator.R;
 import org.solovyev.android.calculator.RemovalConfirmationDialog;
+import org.solovyev.android.calculator.databinding.FragmentPlotFunctionEditBinding;
 import org.solovyev.android.calculator.functions.BaseFunctionFragment;
 import org.solovyev.android.calculator.functions.CppFunction;
 import org.solovyev.android.plotter.Color;
@@ -30,7 +31,6 @@ import java.util.List;
 import javax.annotation.Nonnull;
 import javax.inject.Inject;
 
-import butterknife.BindView;
 import jscl.math.function.CustomFunction;
 import uz.shift.colorpicker.LineColorPicker;
 import uz.shift.colorpicker.OnColorChangedListener;
@@ -39,17 +39,11 @@ public class PlotEditFunctionFragment extends BaseFunctionFragment
     implements SeekBar.OnSeekBarChangeListener {
     @Inject
     Plotter plotter;
-    @BindView(R.id.fn_meshspec_views)
     View meshSpecViews;
-    @BindView(R.id.fn_color_label)
     TextView colorLabel;
-    @BindView(R.id.fn_color_picker)
     LineColorPicker colorPicker;
-    @BindView(R.id.fn_linewidth_label)
     TextView lineWidthLabel;
-    @BindView(R.id.fn_linewidth_seekbar)
     SeekBar lineWidthSeekBar;
-    @BindView(R.id.fn_iconview)
     PlotIconView iconView;
     private PlotFunction plotFunction;
 
@@ -101,6 +95,13 @@ public class PlotEditFunctionFragment extends BaseFunctionFragment
     protected View onCreateDialogView(@NonNull Context context, @NonNull LayoutInflater inflater,
         @Nullable Bundle savedInstanceState) {
         final View view = super.onCreateDialogView(context, inflater, savedInstanceState);
+        FragmentPlotFunctionEditBinding binding = FragmentPlotFunctionEditBinding.bind(view);
+        meshSpecViews = binding.fnMeshspecViews;
+        colorLabel = binding.fnColorLabel;
+        colorPicker = binding.fnColorPicker;
+        lineWidthLabel = binding.fnLinewidthLabel;
+        lineWidthSeekBar = binding.fnLinewidthSeekbar;
+        iconView = binding.fnIconview;
         colorPicker.setOnColorChangedListener(new OnColorChangedListener() {
             @Override
             public void onColorChanged(int c) {

app/src/main/java/org/solovyev/android/calculator/plot/PlotFunctionsFragment.java

@@ -1,6 +1,5 @@
 package org.solovyev.android.calculator.plot;
 
-import static android.support.v7.widget.LinearLayoutManager.VERTICAL;
 import static android.view.Menu.NONE;
 
 import android.annotation.SuppressLint;
@@ -8,13 +7,8 @@ import android.content.Context;
 import android.content.DialogInterface;
 import android.graphics.Typeface;
 import android.os.Bundle;
-import android.support.annotation.NonNull;
-import android.support.annotation.Nullable;
-import android.support.v4.app.FragmentManager;
-import android.support.v7.app.AlertDialog;
-import android.support.v7.widget.DividerItemDecoration;
-import android.support.v7.widget.LinearLayoutManager;
-import android.support.v7.widget.RecyclerView;
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
 import android.view.ContextMenu;
 import android.view.LayoutInflater;
 import android.view.MenuItem;
@@ -22,11 +16,17 @@ import android.view.View;
 import android.view.ViewGroup;
 import android.widget.TextView;
 
+import androidx.appcompat.app.AlertDialog;
+import androidx.fragment.app.FragmentManager;
+import androidx.recyclerview.widget.DividerItemDecoration;
+import androidx.recyclerview.widget.LinearLayoutManager;
+import androidx.recyclerview.widget.RecyclerView;
 import org.solovyev.android.calculator.App;
 import org.solovyev.android.calculator.AppComponent;
 import org.solovyev.android.calculator.BaseActivity;
 import org.solovyev.android.calculator.BaseDialogFragment;
 import org.solovyev.android.calculator.R;
+import org.solovyev.android.calculator.databinding.FragmentFunctionsFunctionBinding;
 import org.solovyev.android.plotter.BasePlotterListener;
 import org.solovyev.android.plotter.PlotFunction;
 import org.solovyev.android.plotter.PlotIconView;
@@ -37,8 +37,6 @@ import java.util.List;
 import javax.annotation.Nonnull;
 import javax.inject.Inject;
 
-import butterknife.BindView;
-import butterknife.ButterKnife;
 
 public class PlotFunctionsFragment extends BaseDialogFragment {
 
@@ -75,7 +73,7 @@ public class PlotFunctionsFragment extends BaseDialogFragment {
     protected RecyclerView onCreateDialogView(@NonNull Context context, @NonNull LayoutInflater inflater, Bundle savedInstanceState) {
         @SuppressLint("InflateParams") final RecyclerView view = (RecyclerView) inflater.inflate(R.layout.fragment_plot_functions, null);
 
-        view.setLayoutManager(new LinearLayoutManager(context, VERTICAL, false));
+        view.setLayoutManager(new LinearLayoutManager(context, RecyclerView.VERTICAL, false));
         view.addItemDecoration(new DividerItemDecoration(context, DividerItemDecoration.VERTICAL));
         adapter = new Adapter(plotter.getPlotData().functions);
         view.setAdapter(adapter);
@@ -107,17 +105,16 @@ public class PlotFunctionsFragment extends BaseDialogFragment {
 
     public class ViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener, View.OnCreateContextMenuListener, MenuItem.OnMenuItemClickListener {
 
-        @BindView(R.id.function_icon)
         PlotIconView icon;
 
-        @BindView(R.id.function_name)
         TextView name;
         private PlotFunction function;
 
-        private ViewHolder(@NonNull View itemView) {
-            super(itemView);
+        private ViewHolder(@NonNull FragmentFunctionsFunctionBinding binding) {
+            super(binding.getRoot());
             BaseActivity.fixFonts(itemView, typeface);
-            ButterKnife.bind(this, itemView);
+            icon = binding.functionIcon;
+            name = binding.functionName;
             itemView.setOnClickListener(this);
             itemView.setOnCreateContextMenuListener(this);
         }
@@ -159,7 +156,7 @@ public class PlotFunctionsFragment extends BaseDialogFragment {
         @Override
         public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
             final LayoutInflater inflater = LayoutInflater.from(parent.getContext());
-            return new ViewHolder(inflater.inflate(R.layout.fragment_functions_function, parent, false));
+            return new ViewHolder(FragmentFunctionsFunctionBinding.inflate(inflater, parent, false));
         }
 
         @Override

app/src/main/java/org/solovyev/android/calculator/preferences/NumberFormatExamplesPreference.java

@@ -4,10 +4,11 @@ import android.content.Context;
 import android.graphics.Typeface;
 import android.util.AttributeSet;
 import android.view.View;
-import android.view.ViewGroup;
 import android.widget.TextView;
+import androidx.annotation.NonNull;
+import androidx.preference.Preference;
+import androidx.preference.PreferenceViewHolder;
 import jscl.JsclMathEngine;
-import org.solovyev.android.material.preferences.Preference;
 
 @SuppressWarnings("unused")
 public class NumberFormatExamplesPreference extends Preference {
@@ -45,15 +46,14 @@ public class NumberFormatExamplesPreference extends Preference {
     }
 
     @Override
-    protected View onCreateView(ViewGroup parent) {
-        final View view = super.onCreateView(parent);
-        final View summary = view.findViewById(android.R.id.summary);
+    public void onBindViewHolder(@NonNull PreferenceViewHolder holder) {
+        super.onBindViewHolder(holder);
+        final View summary = holder.findViewById(android.R.id.summary);
         if (summary instanceof TextView) {
             final TextView textView = (TextView) summary;
             textView.setMaxLines(12);
             textView.setLines(12);
             textView.setTypeface(Typeface.MONOSPACE);
         }
-        return view;
     }
 }

app/src/main/java/org/solovyev/android/calculator/preferences/PrecisionPreference.java

@@ -1,26 +1,83 @@
 package org.solovyev.android.calculator.preferences;
 
+import static org.solovyev.common.NumberFormatter.MAX_PRECISION;
+import static org.solovyev.common.NumberFormatter.MIN_PRECISION;
 import android.annotation.TargetApi;
 import android.content.Context;
 import android.content.SharedPreferences;
 import android.os.Build;
-import android.preference.DialogPreference;
+import android.os.Bundle;
 import android.util.AttributeSet;
 import android.view.View;
-import butterknife.BindView;
-import butterknife.ButterKnife;
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import androidx.preference.DialogPreference;
+import androidx.preference.PreferenceDialogFragmentCompat;
 import org.solovyev.android.calculator.Engine;
 import org.solovyev.android.calculator.R;
 import org.solovyev.android.views.DiscreteSeekBar;
 
-import static org.solovyev.common.NumberFormatter.MAX_PRECISION;
-import static org.solovyev.common.NumberFormatter.MIN_PRECISION;
-
 @SuppressWarnings("unused")
 public class PrecisionPreference extends DialogPreference {
 
-    @BindView(R.id.precision_seekbar)
-    DiscreteSeekBar seekBar;
+    public static class Dialog extends PreferenceDialogFragmentCompat {
+        private static final String SAVE_STATE_PRECISION = "PrecisionPreferenceDialog.precision";
+
+        private DiscreteSeekBar seekBar;
+        private int precision;
+
+        public Dialog() {
+            final Bundle args = new Bundle();
+            args.putString(ARG_KEY, Engine.Preferences.Output.precision.getKey());
+            setArguments(args);
+        }
+
+        @Override
+        public void onSaveInstanceState(@NonNull Bundle outState) {
+            super.onSaveInstanceState(outState);
+            if (seekBar != null) {
+                outState.putInt(SAVE_STATE_PRECISION, seekBar.getCurrentTick() + 1);
+            }
+        }
+
+        @Override
+        public void onCreate(@Nullable Bundle savedInstanceState) {
+            super.onCreate(savedInstanceState);
+            if (savedInstanceState == null) {
+                precision = readPrecision();
+            } else {
+                precision = savedInstanceState.getInt(SAVE_STATE_PRECISION, readPrecision());
+            }
+        }
+
+        @Override
+        protected void onBindDialogView(@NonNull View view) {
+            super.onBindDialogView(view);
+            seekBar = (DiscreteSeekBar) view.findViewById(R.id.precision_seekbar);
+
+            seekBar.setMax(MAX_PRECISION - 1);
+            seekBar.setCurrentTick(precision - 1);
+        }
+
+        private int readPrecision() {
+            final DialogPreference preference = getPreference();
+            final SharedPreferences preferences = preference.getSharedPreferences();
+            return Math.max(MIN_PRECISION, Math.min(MAX_PRECISION, Engine.Preferences.Output.precision.getPreference(preferences)));
+        }
+
+        @Override
+        public void onDialogClosed(boolean save) {
+            if (!save) return;
+            final int precision = seekBar.getCurrentTick() + 1;
+            final DialogPreference preference = getPreference();
+            if (preference.callChangeListener(precision)) {
+                final SharedPreferences preferences = preference.getSharedPreferences();
+                final SharedPreferences.Editor editor = preferences.edit();
+                Engine.Preferences.Output.precision.putPreference(editor, precision);
+                editor.apply();
+            }
+        }
+    }
 
     {
         setPersistent(false);
@@ -44,29 +101,4 @@ public class PrecisionPreference extends DialogPreference {
     public PrecisionPreference(Context context) {
         super(context);
     }
-
-    @Override
-    protected void onBindDialogView(View view) {
-        super.onBindDialogView(view);
-        ButterKnife.bind(this, view);
-
-        final SharedPreferences preferences = getSharedPreferences();
-        seekBar.setMax(MAX_PRECISION - 1);
-        final int precision = Math.max(MIN_PRECISION, Math.min(MAX_PRECISION, Engine.Preferences.Output.precision.getPreference(preferences)));
-        seekBar.setCurrentTick(precision - 1);
-    }
-
-    @Override
-    protected void onDialogClosed(boolean save) {
-        super.onDialogClosed(save);
-        if (!save) {
-            return;
-        }
-        final int precision = seekBar.getCurrentTick() + 1;
-        if (callChangeListener(precision)) {
-            final SharedPreferences.Editor editor = getSharedPreferences().edit();
-            Engine.Preferences.Output.precision.putPreference(editor, precision);
-            editor.apply();
-        }
-    }
 }

app/src/main/java/org/solovyev/android/calculator/preferences/PreferenceEntry.java

@@ -1,7 +1,7 @@
 package org.solovyev.android.calculator.preferences;
 
 import android.content.Context;
-import android.support.annotation.NonNull;
+import androidx.annotation.NonNull;
 
 public interface PreferenceEntry {
     @NonNull

app/src/main/java/org/solovyev/android/calculator/preferences/PreferencesActivity.java

@@ -4,9 +4,9 @@ import android.content.Context;
 import android.content.Intent;
 import android.content.SharedPreferences;
 import android.os.Bundle;
-import android.support.annotation.NonNull;
-import android.support.annotation.StringRes;
-import android.support.annotation.XmlRes;
+import androidx.annotation.NonNull;
+import androidx.annotation.StringRes;
+import androidx.annotation.XmlRes;
 import android.util.SparseArray;
 
 import org.solovyev.android.calculator.App;
@@ -81,7 +81,7 @@ public class PreferencesActivity extends BaseActivity implements SharedPreferenc
         if (savedInstanceState == null) {
             final int preference = intent.getIntExtra(EXTRA_PREFERENCE, R.xml.preferences);
             getSupportFragmentManager().beginTransaction()
-                    .add(R.id.main, PreferencesFragment.create(preference, R.layout.fragment_preferences))
+                    .add(R.id.main, PreferencesFragment.create(preference))
                     .commit();
         }
 

app/src/main/java/org/solovyev/android/calculator/preferences/PreferencesFragment.java

@@ -5,22 +5,31 @@ import static org.solovyev.android.calculator.Engine.Preferences.angleUnitName;
 import static org.solovyev.android.calculator.Engine.Preferences.numeralBaseName;
 import static org.solovyev.android.calculator.wizard.CalculatorWizards.DEFAULT_WIZARD_FLOW;
 import static org.solovyev.android.wizard.WizardUi.startWizard;
-
 import android.content.Context;
 import android.content.Intent;
 import android.content.SharedPreferences;
-import android.os.Build;
 import android.os.Bundle;
-import android.preference.ListPreference;
-import android.preference.Preference;
-import android.support.v4.app.FragmentActivity;
 import android.util.SparseArray;
 import android.view.View;
-import android.widget.ListView;
-
+import android.view.ViewGroup;
+import android.view.ViewParent;
+import androidx.annotation.NonNull;
+import androidx.fragment.app.FragmentActivity;
+import androidx.preference.ListPreference;
+import androidx.preference.Preference;
+import androidx.preference.PreferenceDialogFragmentCompat;
+import androidx.preference.PreferenceFragmentCompat;
+import androidx.recyclerview.widget.RecyclerView;
 import com.squareup.otto.Bus;
 import com.squareup.otto.Subscribe;
-
+import java.util.Arrays;
+import java.util.List;
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+import javax.inject.Inject;
+import jscl.AngleUnit;
+import jscl.JsclMathEngine;
+import jscl.NumeralBase;
 import org.solovyev.android.calculator.ActivityLauncher;
 import org.solovyev.android.calculator.AdView;
 import org.solovyev.android.calculator.Engine;
@@ -38,20 +47,11 @@ import org.solovyev.android.prefs.StringPreference;
 import org.solovyev.android.wizard.Wizards;
 import org.solovyev.common.text.CharacterMapper;
 
-import java.util.Arrays;
-import java.util.List;
 
-import javax.annotation.Nonnull;
-import javax.annotation.Nullable;
-import javax.inject.Inject;
+public class PreferencesFragment extends PreferenceFragmentCompat implements SharedPreferences.OnSharedPreferenceChangeListener {
+    @Nonnull
+    private static String ARG_PREFERENCES = "preferences";
 
-import jscl.AngleUnit;
-import jscl.JsclMathEngine;
-import jscl.NumeralBase;
-
-public class PreferencesFragment extends org.solovyev.android.material.preferences.PreferencesFragment implements SharedPreferences.OnSharedPreferenceChangeListener {
-
-    private static boolean SUPPORT_HEADERS = Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB;
     @Nullable
     private AdView adView;
     @Inject
@@ -70,9 +70,11 @@ public class PreferencesFragment extends org.solovyev.android.material.preferenc
     Bus bus;
 
     @Nonnull
-    public static PreferencesFragment create(int preferences, int layout) {
+    public static PreferencesFragment create(int preferences) {
         final PreferencesFragment fragment = new PreferencesFragment();
-        fragment.setArguments(createArguments(preferences, layout, NO_THEME));
+        final Bundle args = new Bundle();
+        args.putInt(ARG_PREFERENCES, preferences);
+        fragment.setArguments(args);
         return fragment;
     }
 
@@ -85,6 +87,12 @@ public class PreferencesFragment extends org.solovyev.android.material.preferenc
         bus.register(this);
     }
 
+    @Override
+    public void onCreatePreferences(@androidx.annotation.Nullable Bundle savedInstanceState, @androidx.annotation.Nullable String rootKey) {
+        int preferencesResId = getArguments().getInt(ARG_PREFERENCES);
+        addPreferencesFromResource(preferencesResId);
+    }
+
     private void setPreferenceIntent(int xml, @Nonnull PreferencesActivity.PrefDef def) {
         final Preference preference = findPreference(def.id);
         if (preference != null) {
@@ -96,11 +104,26 @@ public class PreferencesFragment extends org.solovyev.android.material.preferenc
         }
     }
 
+    /** @noinspection deprecation*/
+    @Override
+    public void onDisplayPreferenceDialog(@NonNull Preference preference) {
+        String fragmentTag = "fragment:" + preference.getKey();
+        if (getParentFragmentManager().findFragmentByTag(fragmentTag) != null) return;
+
+        if (preference instanceof PrecisionPreference) {
+            final PreferenceDialogFragmentCompat f = new PrecisionPreference.Dialog();
+            f.setTargetFragment(this, 0);
+            f.show(getParentFragmentManager(), fragmentTag);
+        } else {
+            super.onDisplayPreferenceDialog(preference);
+        }
+    }
+
     @Override
     public void onViewCreated(View view, Bundle savedInstanceState) {
         super.onViewCreated(view, savedInstanceState);
 
-        final int preference = getPreferencesResId();
+        final int preference = getArguments().getInt(ARG_PREFERENCES);
         if (preference == R.xml.preferences) {
             prepareScreens();
             prepareIntroduction();
@@ -200,7 +223,7 @@ public class PreferencesFragment extends org.solovyev.android.material.preferenc
     }
 
     private void prepareNumberFormatExamplesPreference() {
-        final NumberFormatExamplesPreference preference = (NumberFormatExamplesPreference) preferenceManager.findPreference("numberFormat.examples");
+        final NumberFormatExamplesPreference preference = (NumberFormatExamplesPreference) getPreferenceManager().findPreference("numberFormat.examples");
         if (preference == null) {
             return;
         }
@@ -208,7 +231,7 @@ public class PreferencesFragment extends org.solovyev.android.material.preferenc
     }
 
     private void prepareSeparatorPreference() {
-        final ListPreference preference = (ListPreference) preferenceManager.findPreference(Engine.Preferences.Output.separator.getKey());
+        final ListPreference preference = (ListPreference) getPreferenceManager().findPreference(Engine.Preferences.Output.separator.getKey());
         preference.setSummary(separatorName(Engine.Preferences.Output.separator.getPreference(preferences)));
         preference.setOnPreferenceChangeListener(new Preference.OnPreferenceChangeListener() {
             @Override
@@ -232,7 +255,7 @@ public class PreferencesFragment extends org.solovyev.android.material.preferenc
     }
 
     private void preparePrecisionPreference() {
-        final PrecisionPreference preference = (PrecisionPreference) preferenceManager.findPreference(Engine.Preferences.Output.precision.getKey());
+        final PrecisionPreference preference = (PrecisionPreference) getPreferenceManager().findPreference(Engine.Preferences.Output.precision.getKey());
         preference.setSummary(String.valueOf(Engine.Preferences.Output.precision.getPreference(preferences)));
         preference.setOnPreferenceChangeListener(new Preference.OnPreferenceChangeListener() {
             @Override
@@ -244,7 +267,7 @@ public class PreferencesFragment extends org.solovyev.android.material.preferenc
     }
 
     private <E extends Enum<E> & PreferenceEntry> void prepareListPreference(@Nonnull final StringPreference<E> p, @Nonnull Class<E> type) {
-        final ListPreference preference = (ListPreference) preferenceManager.findPreference(p.getKey());
+        final ListPreference preference = (ListPreference) getPreferenceManager().findPreference(p.getKey());
         if (preference == null) {
             return;
         }
@@ -267,7 +290,7 @@ public class PreferencesFragment extends org.solovyev.android.material.preferenc
     }
 
     private void prepareMode() {
-        final ListPreference mode = (ListPreference) preferenceManager.findPreference(Preferences.Gui.mode.getKey());
+        final ListPreference mode = (ListPreference) getPreferenceManager().findPreference(Preferences.Gui.mode.getKey());
         mode.setSummary(Preferences.Gui.getMode(preferences).name);
         mode.setOnPreferenceChangeListener(new Preference.OnPreferenceChangeListener() {
             @Override
@@ -279,7 +302,7 @@ public class PreferencesFragment extends org.solovyev.android.material.preferenc
     }
 
     private void prepareAngles() {
-        final ListPreference angles = (ListPreference) preferenceManager.findPreference(Engine.Preferences.angleUnit.getKey());
+        final ListPreference angles = (ListPreference) getPreferenceManager().findPreference(Engine.Preferences.angleUnit.getKey());
         angles.setSummary(angleUnitName(Engine.Preferences.angleUnit.getPreference(preferences)));
         angles.setOnPreferenceChangeListener(new Preference.OnPreferenceChangeListener() {
             @Override
@@ -291,7 +314,7 @@ public class PreferencesFragment extends org.solovyev.android.material.preferenc
     }
 
     private void prepareRadix() {
-        final ListPreference radix = (ListPreference) preferenceManager.findPreference(Engine.Preferences.numeralBase.getKey());
+        final ListPreference radix = (ListPreference) getPreferenceManager().findPreference(Engine.Preferences.numeralBase.getKey());
         radix.setSummary(numeralBaseName(Engine.Preferences.numeralBase.getPreference(preferences)));
         radix.setOnPreferenceChangeListener(new Preference.OnPreferenceChangeListener() {
             @Override
@@ -306,7 +329,7 @@ public class PreferencesFragment extends org.solovyev.android.material.preferenc
         if (preference != R.xml.preferences_appearance) {
             return;
         }
-        final ListPreference theme = (ListPreference) preferenceManager.findPreference(Preferences.Gui.theme.getKey());
+        final ListPreference theme = (ListPreference) getPreferenceManager().findPreference(Preferences.Gui.theme.getKey());
         final FragmentActivity context = getActivity();
         populate(theme,
                 Theme.material_theme,
@@ -349,7 +372,7 @@ public class PreferencesFragment extends org.solovyev.android.material.preferenc
             return;
         }
 
-        final ListPreference language = (ListPreference) preferenceManager.findPreference(Preferences.Gui.language.getKey());
+        final ListPreference language = (ListPreference) getPreferenceManager().findPreference(Preferences.Gui.language.getKey());
         populate(language, languages.getList());
         language.setSummary(languages.getCurrent().getName(getActivity()));
         language.setOnPreferenceChangeListener(new Preference.OnPreferenceChangeListener() {
@@ -417,38 +440,24 @@ public class PreferencesFragment extends org.solovyev.android.material.preferenc
         super.onDestroy();
     }
 
-    private boolean supportsHeaders() {
-        return SUPPORT_HEADERS;
-    }
 
     protected void onShowAd(boolean show) {
-        if (!supportsHeaders()) {
-            return;
-        }
         if (getView() == null) {
             return;
         }
 
-        final ListView listView = getListView();
+        final View root = getView();
+        if (!(root instanceof ViewGroup)) return;
+
+        final ViewGroup container = (ViewGroup) root;
         if (show) {
-            if (adView != null) {
-                return;
-            }
+            if (adView != null) return;
             adView = new AdView(getActivity());
             adView.show();
-            try {
-                listView.addHeaderView(adView);
-            } catch (IllegalStateException e) {
-                // doesn't support header views
-                SUPPORT_HEADERS = false;
-                adView.hide();
-                adView = null;
-            }
+            container.addView(adView);
         } else {
-            if (adView == null) {
-                return;
-            }
-            listView.removeHeaderView(adView);
+            if (adView == null) return;
+            container.removeView(adView);
             adView.hide();
             adView = null;
         }

app/src/main/java/org/solovyev/android/calculator/preferences/PurchaseDialogActivity.java

@@ -28,11 +28,11 @@ import android.app.Activity;
 import android.content.DialogInterface;
 import android.content.Intent;
 import android.os.Bundle;
-import android.support.annotation.NonNull;
-import android.support.v4.app.Fragment;
-import android.support.v7.app.AlertDialog;
-import android.support.v7.app.AppCompatActivity;
+import androidx.annotation.NonNull;
 
+import androidx.appcompat.app.AlertDialog;
+import androidx.appcompat.app.AppCompatActivity;
+import androidx.fragment.app.Fragment;
 import org.solovyev.android.calculator.App;
 import org.solovyev.android.calculator.BaseDialogFragment;
 import org.solovyev.android.calculator.R;

app/src/main/java/org/solovyev/android/calculator/release/ChooseThemeReleaseNoteStep.java

@@ -1,8 +1,8 @@
 package org.solovyev.android.calculator.release;
 
 import android.os.Bundle;
-import android.support.v4.app.Fragment;
 
+import androidx.fragment.app.Fragment;
 import javax.annotation.Nonnull;
 
 public class ChooseThemeReleaseNoteStep extends ReleaseNoteStep {